The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero

(southeastern Sicily) and Adria (La Queglia and Pietre Nere southern Italy)

geochemical and isotopic evidence against a plume-related origin

of circum-Mediterranean magmas

RICCARDO AVANZINELLI1 GIOVANNA T SAPIENZA23 and SANDRO CONTICELLI14

1 Dipartimento di Scienze della Terra Universita degli Studi di Firenze Via Giorgio La Pira 4 50121 Firenze ItalyCorresponding author e-mail riccardoavanzinelliunifiit

2 Dipartimento di Scienze della Terra e Geologico-Ambientali Universita di Bologna Piazza di Porta San Donato 140126 Bologna Italy

3 now at Schlumberger Italiana SpA Via dellrsquoUnione Europea 6A - Torre Alfa 20097 San Donato Milanese Italy4 Istituto di Geoscienze e Georisorse UO di Firenze Consiglio Nazionale delle Ricerche Via Giorgio La Pira 4 50121

Firenze Italy

Abstract The Pachino-Capo Passero centre located at the south-easternmost portion of Sicily represents an Upper Cretaceousvolcano within the Pelagian Block a fragment in lithospheric continuity with the African Plate The volcanic rocks of the Pachino-Capo Passero centre show fairly homogeneous mafic characteristics with a typical within-plate signature Two groups with differentlevels of alkali and incompatible trace element enrichment have been recognised Trace element modelling indicates that the twogroups might be originated at different degrees of partial melting The geochemical data suggest that Cretaceous rocks of Pachino-Capo Passero originated at greater depth than the neighbouring Neogene volcanic products of the Hyblean Plateau likely from anasthenospheric mantle source Sr-Nd-Pb isotope compositions of Pachino-Capo Passero rocks are presented along with those ofPaleocene and Eocene lamprophyric dikes and small intrusive bodies from the adjacent Adria block now representing the Apulianforeland (ie Pietre Nere and La Queglia dykes) in the context of investigating the presence and origin of a Common MantleReservoir beneath the Central Mediterranean area The Sr-Nd-Pb isotopes of the Pachino-Capo Passero rocks are extremely similar tothe recently redefined FOZO component whilst other suites (ie Pietre Nere) might require additional enriched components Highlyradiogenic Pb isotopes along with high TiO2 contents and fractionated MREEHREE argue for the presence of significant amount ofrecycled mafic oceanic crust in the mantle sources of these magmas as eclogitic lithologies dispersed within a depleted peridotiticmantle The Sr-Nd-Pb isotope compositions of the studied rocks are also compared with literature data from the Canary Islands asrepresentative of a putative plume component contaminating the mantle region The data show a clear distinction especially in D74vs D84 indicating that the age and composition of the mafic crust recycled within the source of Pachino-Capo Passero rocks must beolder and bear higher time-integrated UTh ratios The geochemical and isotope composition of Pachino-Capo Passero magmasPietre Nere and La Queglia is interpreted as a feature of the ambient asthenospheric mantle due to the extremely widespread processof prolonged subduction and recycling of mafic oceanic crust of variable age and composition Therefore no need for a uniquereservoir related to a mantle plume is envisaged

Key-words Sr-Nd-Pb isotope trace elements HIMU FOZO Common Mantle Reservoir European asthenospheric mantlePachino-Capo Passero volcano La Queglia Pietre Nere

1 Introduction

In the last two decades a number of authors (eg Worneret al 1986 Wilson amp Downes 1991 1992 Cebria ampWilson 1995 Granet et al 1995 Hoernle et al 1995

Wilson amp Patterson 2001 Lustrino amp Wilson 2007Piromallo et al 2008) have suggested the existence of acommon and geochemically relatively uniform mantlesource for within-plate magmas erupted in the circum-Mediterranean and neighbouring areas According to thisinterpretation this mantle reservoir alternatively calledPREMA (PREvalent MAntle Worner et al 1986)Component A (Wilson amp Downes 1991 1992) LVC

Giovanna Sapienza and Riccardo Avanzinelli equally contributed to thispaper

0935-1221120024-2185 $ 1080DOI 1011270935-122120120024-2185 2011 E Schweizerbartrsquosche Verlagsbuchhandlung D-70176 Stuttgart

Eur J Mineral

2012 24 73ndash96

Published online November 2011

(Low Velocity Component Hoernle et al 1995) EAR(European Asthenospheric Reservoir Cebria amp Wilson1995 Granet et al 1995) CEA (Central EuropeanAnomaly Goes et al 1999) or CMR (Common MantleReservoir Lustrino amp Wilson 2007) has been intermit-tently sampled from the Cenozoic to the present time byseveral volcanoes in the area

Some authors have related this source to the upwellingof a lower-mantle plume beneath Europe and the easternNorth Atlantic (eg Hoernle et al 1995 Goes et al 1999Bell et al 2004) and variously associated this plume withthe Canary andor Cape Verde Islands (eg Cebria ampLopez-Ruiz 1995 Oyarzun et al 1997 Piromallo et al2008) and Iceland (eg Bijwaard amp Spakman 1999Wilson amp Patterson 2001) Others have suggested thatmagmatism in this wide area is related to various geody-namic settings related to lithospheric extension continen-tal collision and orogenic collapse and contemporaneoussubduction slab roll-back and slab-window formation(Lustrino amp Wilson 2007)

The magmatism of the south-eastern area of Sicily (ieHyblean Plateau) represents an important end-member toinvestigate the possible existence and nature of the com-mon mantle component Hyblean Neogene magmatism hasbeen the object of several petrologic studies (eg Carter ampCivetta 1977 Tonarini et al 1996 Beccaluva et al 1998Bianchini et al 1998 1999 2010 Trua et al 1998) Bycontrast the oldest outcropping volcanic rocks of south-eastern Sicily the Cretaceous lavas of the Pachino-CapoPassero area have never been studied in detail A fewgeochemical and isotopic data of these products are avail-able only in some general studies along with more recentHyblean products (Carter amp Civetta 1977 Rocchi et al1998 Beccaluva et al 2007)

In this paper we present new mineralogical geochem-ical and Sr-Nd-Pb isotopic data obtained on selected sam-ples of Pachino-Capo Passero volcanic rocks with the aimof defining the isotopic and geochemical signatures of theirmantle source within the framework of the geodynamicevolution of the area The geochemical and isotopic data ofPachino-Capo Passero volcanic products will be discussedin relationship to the Neogene magmatism of the HybleanPlateau but also to the Na-alkaline lamprophyric dykes ofPietre Nere and La Queglia These two small outcropsrepresent the magmatic activity occurring in the neigh-bouring Adria plate during the Paleogene and Eocenewithin a geodynamic setting similar to that of SE SicilyTherefore they might represent an interesting comparisonof the processes of magma genesis during the time gapoccurring between the Pachino-Capo Passero products andthe more recent Neogene Hyblean Plateau magmas

2 Geological and volcanological outlines

The Hyblean Plateau (south-eastern Sicily Italy) islocated in the Central Mediterranean a geodynamicallycomplex area controlled by the convergence between the

European and the African Plates (eg Dewey et al 1989)Intense magmatic activity affected the Plateau since atleast Triassic time (Cristofolini 1966) producing signifi-cant crustal thickening as evidenced by geophysical inves-tigations (Arisi Rota amp Fichera 1987 Ben-Avraham ampGrasso 1990) Furthermore traces of Permo-Triassic mag-matism have been recognised in petrological studies ofgabbroic xenoliths erupted by Upper Miocene explosivemagmatism (Sapienza et al 2009)

The Hyblean Plateau (SE Sicily southern Italy Fig 1) isconsidered to represent the northernmost portion of thePelagian Block in lithospheric continuity with theAfrican Plate (Bianchi et al 1987) Since the late

10deg 20deg 30deg 40deg

45deg

35deg

40deg

30deg

0deg

Upper Cretaceous maficlavas and dikes

Lutetian limestones

Upper Cretaceous reeflimestones with Rudistis

Messinian marls

Lower and Middle Pliocenemarls and calcarenites

Plio-Quaternary deposits

01 02

03 04

05 06 0708 09 10

Pachino

18 19

N

2 km

20

21

15

1716

Portopalo

AcquaPalomba

Czo S Lucia

A

B

C

Appenninic-Maghrebiannappes

Kabilo-Calabride nappes

Sicanian nappes

Strike-slip direction

Main fault system

AB Apulian BlockCA Calabrian ArcME Malta Escarpment

Eruptive center Supposed eruptive center

141311 12

AB

Tyrrenian basin

Sar

dini

a

Pelagian block

ME

SouthernAppennine

CA

SicilyIonianBasin

PNLQ

Capo Passero

Fig 1 (a) Map of the Central Mediterranean area with location ofPietre Nere (PN) and La Queglia (LQ) (b) Main structural domainsof the studied area (simplified after Lentini et al (1996)) (c)Geological sketch-map of the Pachino-Capo Passero areaNumbers indicate the sampling sites Eruptive (including the sup-posed) centres are from Carveni et al (1991)

74 R Avanzinelli GT Sapienza S Conticelli

Cretaceous-Paleocene Africa and Eurasia both movednorth-eastward Plate motions as recorded in southAtlantic seamount ages (OrsquoConnor et al 1999) and inthe migration of magmatism along the African Rift(George et al 1998) imply rates on the order of 3 cmyrover the past 45 Ma consistent with anti-clockwise rota-tion of the African Plate about a pole of rotation near theCanary Islands Similarly Faccenna et al (2003) suggestthat Africa moved at a rate which decreased from 3 toabout 1 cmyr in the last 35 Ma whilst Eurasia kept aroughly constant rate of 1 cmyr (Faccenna et al 2003)According to these data and to palaeogeographic recon-structions (Stampfli amp Borel 2002 Piromallo et al 2008)the position of the Pelagian Block in the Upper Cretaceousshould have been 2000 km SE of its present position

The Pelagian Block consists of a 10 km-thickMesozoic-Cenozoic platform-type carbonate sequenceand Neogene-Quaternary silici-clastics sedimentary rockssit on top of a continental lithosphere of Proterozoic toArchean age (Sapienza et al 2007) The present-dayMoho underneath the Hyblean Plateau is located at25ndash30 km (075ndash085 GPa Scarascia et al 1994)Geophysical (Arisi Rota amp Fichera 1987 Ben-Avrahamamp Grasso 1990) and petrological (Sapienza amp Scribano2000) studies are consistent with the presence of a largemafic body underneath the Hyblean Plateau testifying tothe intense magmatic activity that modified the Hybleanlithosphere through time

Several volcanic layers interrupt the sedimentarysequence at least since Triassic time (as provided by datafrom commercial drill holes Cristofolini 1966 Pataccaet al 1979) Three magmatic episodes are exposed on thesurface Cretaceous alkali-basalts (Amore et al 1988Longaretti amp Rocchi 1990 Carveni et al 1991 Rocchiet al 1998) Miocene alkali-basaltic and nephelinitic lavasand tuff-breccia pipes (Carbone amp Lentini 1981Bianchini et al 1998 1999) and Plio-Pleistocene tholeii-tic to nephelinitic lava flows (Beccaluva et al 1998Bianchini et al 1998 1999 Trua et al 1998) Thesemagmatic events are characterized by a northward migra-tion through time (Bianchi et al 1987)

The Pachino-Capo Passero volcano is located at theextreme south-eastern tip of Sicily (Fig 1) where volcan-ism took place during the Upper Cretaceous (Carboneet al 1982) KAr ages for this products range from 704to 841 Ma (Barberi et al 1974) although the authorssuggest the most reliable age is 71 Ma It represents theoldest magmatic episode of SE Sicily among those definedabove The volcanic sequence is made up by a thick suc-cession of submarine lava flows overlain by coeval shal-low-water carbonate platform (Carbone et al 1982) withthe central portion of the volcanic edifice represented bysub-aerial activity (ie Cozzo Santa Lucia hill Fig 1c)By contrast the presence of whitish carbonate-rich vein-lets cross-cutting the lava level in the peripheral areas(Electronic supplementary material ESM 1a freely avail-able online on the GSW website of the journal at httpeurjmingeoscienceworldorg) may be related to the intru-sion and crystallization of secondary carbonate mud in a

clear submarine environment beneath the carbonate plat-form as evident in the basal level of the volcanic outcrop atthe Acqua Palomba area Carbonate blocks percolated bybasaltic veinlets and micropods do also occur (ESM 1b)The submarine volcanic succession was cut by late dykespossibly related to the subaerial phase of the volcanoThese field data might help to clarify the nature of thevolcanic environment that has being alternatively consid-ered submarine or sub-aerial (eg Amore et al 1988Carveni et al 1991)

The lamprophyric dykes and hypabyssal rocks intrudedin the Adria block are from La Queglia ridge in theAbruzzi region and from Pietre Nere in the Apulian fore-land of the Italian region (eg Bellini 1957 De Fino et al1981 Durazzo et al 1984 Bigazzi et al 1996 Conticelliet al 2002 2007 Vichi et al 2005) The La Queglialamprophyre is intruded within Eocene reef limestonesradiometric dating of the rock provided unreliable datahence the age used in this paper is the maximum onereferred to the age of the intruded formation (eg Bellini1957 Durazzo et al 1984 Vichi et al 2004) The mela-syenite dyke of the Pietre Nere is part of a small intrusivemafic alkaline complex within the Paleocene reef lime-stones of the Gargano promontory in the Apulian region(eg De Fino et al 1981) Dating of these intrusive rocksgave a range from 58 to 65 Ma but the melasyenite studiedin this paper has an age of 622 Ma (Bigazzi et al 1996)Both the lamprophyric dyke and the melasyenite belong tothe Adria block a former portion of the African marginnow detached and isolated from the old continent

3 Sampling and analytical methods

Twenty-one samples from Pachino-Capo Passero volcaniccentre (Fig 1c) two samples from Pietre Nere and foursamples from La Queglia both from the Adria block werecollected The freshest samples among volcanic and sub-volcanic rocks and one reef-limestone from Capo Passerowere finely powdered in an agate mortar for chemicalanalyses In Table 1 the sampling locality latitude andlongitude petrography mineralogy and modal contentsfor the analysed samples are reported Whole-rock major-and trace-elements data (Tables 2 and 3) were acquired atActivation Laboratories (Ancaster ON Canada) viaFusion ICP-OES and ICP-MS respectively Lead wasanalysed by liquid ICP-MS for a better precision andaccuracy at low contents Analytical details can be foundon the website httpwwwactlabscom

Major-element compositions of minerals from five(ESM 2) samples were analysed by JEOL JXA-8600 elec-tron microprobe at CNR-IGG in Florence equipped withfour wave-length-dispersion spectrometers and integratedwith an energy-dispersion spectrometry system Operationconditions were 15 kV accelerating voltage and 10 nAbeam current Spot size is 1 mm Different times forelement collection were applied to the minerals Furtherdetails can be found in Vaggelli et al (1999)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 75

(Low Velocity Component Hoernle et al 1995) EAR(European Asthenospheric Reservoir Cebria amp Wilson1995 Granet et al 1995) CEA (Central EuropeanAnomaly Goes et al 1999) or CMR (Common MantleReservoir Lustrino amp Wilson 2007) has been intermit-tently sampled from the Cenozoic to the present time byseveral volcanoes in the area

Some authors have related this source to the upwellingof a lower-mantle plume beneath Europe and the easternNorth Atlantic (eg Hoernle et al 1995 Goes et al 1999Bell et al 2004) and variously associated this plume withthe Canary andor Cape Verde Islands (eg Cebria ampLopez-Ruiz 1995 Oyarzun et al 1997 Piromallo et al2008) and Iceland (eg Bijwaard amp Spakman 1999Wilson amp Patterson 2001) Others have suggested thatmagmatism in this wide area is related to various geody-namic settings related to lithospheric extension continen-tal collision and orogenic collapse and contemporaneoussubduction slab roll-back and slab-window formation(Lustrino amp Wilson 2007)

The magmatism of the south-eastern area of Sicily (ieHyblean Plateau) represents an important end-member toinvestigate the possible existence and nature of the com-mon mantle component Hyblean Neogene magmatism hasbeen the object of several petrologic studies (eg Carter ampCivetta 1977 Tonarini et al 1996 Beccaluva et al 1998Bianchini et al 1998 1999 2010 Trua et al 1998) Bycontrast the oldest outcropping volcanic rocks of south-eastern Sicily the Cretaceous lavas of the Pachino-CapoPassero area have never been studied in detail A fewgeochemical and isotopic data of these products are avail-able only in some general studies along with more recentHyblean products (Carter amp Civetta 1977 Rocchi et al1998 Beccaluva et al 2007)

In this paper we present new mineralogical geochem-ical and Sr-Nd-Pb isotopic data obtained on selected sam-ples of Pachino-Capo Passero volcanic rocks with the aimof defining the isotopic and geochemical signatures of theirmantle source within the framework of the geodynamicevolution of the area The geochemical and isotopic data ofPachino-Capo Passero volcanic products will be discussedin relationship to the Neogene magmatism of the HybleanPlateau but also to the Na-alkaline lamprophyric dykes ofPietre Nere and La Queglia These two small outcropsrepresent the magmatic activity occurring in the neigh-bouring Adria plate during the Paleogene and Eocenewithin a geodynamic setting similar to that of SE SicilyTherefore they might represent an interesting comparisonof the processes of magma genesis during the time gapoccurring between the Pachino-Capo Passero products andthe more recent Neogene Hyblean Plateau magmas

2 Geological and volcanological outlines

The Hyblean Plateau (south-eastern Sicily Italy) islocated in the Central Mediterranean a geodynamicallycomplex area controlled by the convergence between the

European and the African Plates (eg Dewey et al 1989)Intense magmatic activity affected the Plateau since atleast Triassic time (Cristofolini 1966) producing signifi-cant crustal thickening as evidenced by geophysical inves-tigations (Arisi Rota amp Fichera 1987 Ben-Avraham ampGrasso 1990) Furthermore traces of Permo-Triassic mag-matism have been recognised in petrological studies ofgabbroic xenoliths erupted by Upper Miocene explosivemagmatism (Sapienza et al 2009)

The Hyblean Plateau (SE Sicily southern Italy Fig 1) isconsidered to represent the northernmost portion of thePelagian Block in lithospheric continuity with theAfrican Plate (Bianchi et al 1987) Since the late

10deg 20deg 30deg 40deg

45deg

35deg

40deg

30deg

0deg

Upper Cretaceous maficlavas and dikes

Lutetian limestones

Upper Cretaceous reeflimestones with Rudistis

Messinian marls

Lower and Middle Pliocenemarls and calcarenites

Plio-Quaternary deposits

01 02

03 04

05 06 0708 09 10

Pachino

18 19

N

2 km

20

21

15

1716

Portopalo

AcquaPalomba

Czo S Lucia

A

B

C

Appenninic-Maghrebiannappes

Kabilo-Calabride nappes

Sicanian nappes

Strike-slip direction

Main fault system

AB Apulian BlockCA Calabrian ArcME Malta Escarpment

Eruptive center Supposed eruptive center

141311 12

AB

Tyrrenian basin

Sar

dini

a

Pelagian block

ME

SouthernAppennine

CA

SicilyIonianBasin

PNLQ

Capo Passero

Fig 1 (a) Map of the Central Mediterranean area with location ofPietre Nere (PN) and La Queglia (LQ) (b) Main structural domainsof the studied area (simplified after Lentini et al (1996)) (c)Geological sketch-map of the Pachino-Capo Passero areaNumbers indicate the sampling sites Eruptive (including the sup-posed) centres are from Carveni et al (1991)

74 R Avanzinelli GT Sapienza S Conticelli

Cretaceous-Paleocene Africa and Eurasia both movednorth-eastward Plate motions as recorded in southAtlantic seamount ages (OrsquoConnor et al 1999) and inthe migration of magmatism along the African Rift(George et al 1998) imply rates on the order of 3 cmyrover the past 45 Ma consistent with anti-clockwise rota-tion of the African Plate about a pole of rotation near theCanary Islands Similarly Faccenna et al (2003) suggestthat Africa moved at a rate which decreased from 3 toabout 1 cmyr in the last 35 Ma whilst Eurasia kept aroughly constant rate of 1 cmyr (Faccenna et al 2003)According to these data and to palaeogeographic recon-structions (Stampfli amp Borel 2002 Piromallo et al 2008)the position of the Pelagian Block in the Upper Cretaceousshould have been 2000 km SE of its present position

The Pelagian Block consists of a 10 km-thickMesozoic-Cenozoic platform-type carbonate sequenceand Neogene-Quaternary silici-clastics sedimentary rockssit on top of a continental lithosphere of Proterozoic toArchean age (Sapienza et al 2007) The present-dayMoho underneath the Hyblean Plateau is located at25ndash30 km (075ndash085 GPa Scarascia et al 1994)Geophysical (Arisi Rota amp Fichera 1987 Ben-Avrahamamp Grasso 1990) and petrological (Sapienza amp Scribano2000) studies are consistent with the presence of a largemafic body underneath the Hyblean Plateau testifying tothe intense magmatic activity that modified the Hybleanlithosphere through time

Several volcanic layers interrupt the sedimentarysequence at least since Triassic time (as provided by datafrom commercial drill holes Cristofolini 1966 Pataccaet al 1979) Three magmatic episodes are exposed on thesurface Cretaceous alkali-basalts (Amore et al 1988Longaretti amp Rocchi 1990 Carveni et al 1991 Rocchiet al 1998) Miocene alkali-basaltic and nephelinitic lavasand tuff-breccia pipes (Carbone amp Lentini 1981Bianchini et al 1998 1999) and Plio-Pleistocene tholeii-tic to nephelinitic lava flows (Beccaluva et al 1998Bianchini et al 1998 1999 Trua et al 1998) Thesemagmatic events are characterized by a northward migra-tion through time (Bianchi et al 1987)

The Pachino-Capo Passero volcano is located at theextreme south-eastern tip of Sicily (Fig 1) where volcan-ism took place during the Upper Cretaceous (Carboneet al 1982) KAr ages for this products range from 704to 841 Ma (Barberi et al 1974) although the authorssuggest the most reliable age is 71 Ma It represents theoldest magmatic episode of SE Sicily among those definedabove The volcanic sequence is made up by a thick suc-cession of submarine lava flows overlain by coeval shal-low-water carbonate platform (Carbone et al 1982) withthe central portion of the volcanic edifice represented bysub-aerial activity (ie Cozzo Santa Lucia hill Fig 1c)By contrast the presence of whitish carbonate-rich vein-lets cross-cutting the lava level in the peripheral areas(Electronic supplementary material ESM 1a freely avail-able online on the GSW website of the journal at httpeurjmingeoscienceworldorg) may be related to the intru-sion and crystallization of secondary carbonate mud in a

clear submarine environment beneath the carbonate plat-form as evident in the basal level of the volcanic outcrop atthe Acqua Palomba area Carbonate blocks percolated bybasaltic veinlets and micropods do also occur (ESM 1b)The submarine volcanic succession was cut by late dykespossibly related to the subaerial phase of the volcanoThese field data might help to clarify the nature of thevolcanic environment that has being alternatively consid-ered submarine or sub-aerial (eg Amore et al 1988Carveni et al 1991)

The lamprophyric dykes and hypabyssal rocks intrudedin the Adria block are from La Queglia ridge in theAbruzzi region and from Pietre Nere in the Apulian fore-land of the Italian region (eg Bellini 1957 De Fino et al1981 Durazzo et al 1984 Bigazzi et al 1996 Conticelliet al 2002 2007 Vichi et al 2005) The La Queglialamprophyre is intruded within Eocene reef limestonesradiometric dating of the rock provided unreliable datahence the age used in this paper is the maximum onereferred to the age of the intruded formation (eg Bellini1957 Durazzo et al 1984 Vichi et al 2004) The mela-syenite dyke of the Pietre Nere is part of a small intrusivemafic alkaline complex within the Paleocene reef lime-stones of the Gargano promontory in the Apulian region(eg De Fino et al 1981) Dating of these intrusive rocksgave a range from 58 to 65 Ma but the melasyenite studiedin this paper has an age of 622 Ma (Bigazzi et al 1996)Both the lamprophyric dyke and the melasyenite belong tothe Adria block a former portion of the African marginnow detached and isolated from the old continent

3 Sampling and analytical methods

Twenty-one samples from Pachino-Capo Passero volcaniccentre (Fig 1c) two samples from Pietre Nere and foursamples from La Queglia both from the Adria block werecollected The freshest samples among volcanic and sub-volcanic rocks and one reef-limestone from Capo Passerowere finely powdered in an agate mortar for chemicalanalyses In Table 1 the sampling locality latitude andlongitude petrography mineralogy and modal contentsfor the analysed samples are reported Whole-rock major-and trace-elements data (Tables 2 and 3) were acquired atActivation Laboratories (Ancaster ON Canada) viaFusion ICP-OES and ICP-MS respectively Lead wasanalysed by liquid ICP-MS for a better precision andaccuracy at low contents Analytical details can be foundon the website httpwwwactlabscom

Major-element compositions of minerals from five(ESM 2) samples were analysed by JEOL JXA-8600 elec-tron microprobe at CNR-IGG in Florence equipped withfour wave-length-dispersion spectrometers and integratedwith an energy-dispersion spectrometry system Operationconditions were 15 kV accelerating voltage and 10 nAbeam current Spot size is 1 mm Different times forelement collection were applied to the minerals Furtherdetails can be found in Vaggelli et al (1999)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 75

Cretaceous-Paleocene Africa and Eurasia both movednorth-eastward Plate motions as recorded in southAtlantic seamount ages (OrsquoConnor et al 1999) and inthe migration of magmatism along the African Rift(George et al 1998) imply rates on the order of 3 cmyrover the past 45 Ma consistent with anti-clockwise rota-tion of the African Plate about a pole of rotation near theCanary Islands Similarly Faccenna et al (2003) suggestthat Africa moved at a rate which decreased from 3 toabout 1 cmyr in the last 35 Ma whilst Eurasia kept aroughly constant rate of 1 cmyr (Faccenna et al 2003)According to these data and to palaeogeographic recon-structions (Stampfli amp Borel 2002 Piromallo et al 2008)the position of the Pelagian Block in the Upper Cretaceousshould have been 2000 km SE of its present position

The Pelagian Block consists of a 10 km-thickMesozoic-Cenozoic platform-type carbonate sequenceand Neogene-Quaternary silici-clastics sedimentary rockssit on top of a continental lithosphere of Proterozoic toArchean age (Sapienza et al 2007) The present-dayMoho underneath the Hyblean Plateau is located at25ndash30 km (075ndash085 GPa Scarascia et al 1994)Geophysical (Arisi Rota amp Fichera 1987 Ben-Avrahamamp Grasso 1990) and petrological (Sapienza amp Scribano2000) studies are consistent with the presence of a largemafic body underneath the Hyblean Plateau testifying tothe intense magmatic activity that modified the Hybleanlithosphere through time

Several volcanic layers interrupt the sedimentarysequence at least since Triassic time (as provided by datafrom commercial drill holes Cristofolini 1966 Pataccaet al 1979) Three magmatic episodes are exposed on thesurface Cretaceous alkali-basalts (Amore et al 1988Longaretti amp Rocchi 1990 Carveni et al 1991 Rocchiet al 1998) Miocene alkali-basaltic and nephelinitic lavasand tuff-breccia pipes (Carbone amp Lentini 1981Bianchini et al 1998 1999) and Plio-Pleistocene tholeii-tic to nephelinitic lava flows (Beccaluva et al 1998Bianchini et al 1998 1999 Trua et al 1998) Thesemagmatic events are characterized by a northward migra-tion through time (Bianchi et al 1987)

The Pachino-Capo Passero volcano is located at theextreme south-eastern tip of Sicily (Fig 1) where volcan-ism took place during the Upper Cretaceous (Carboneet al 1982) KAr ages for this products range from 704to 841 Ma (Barberi et al 1974) although the authorssuggest the most reliable age is 71 Ma It represents theoldest magmatic episode of SE Sicily among those definedabove The volcanic sequence is made up by a thick suc-cession of submarine lava flows overlain by coeval shal-low-water carbonate platform (Carbone et al 1982) withthe central portion of the volcanic edifice represented bysub-aerial activity (ie Cozzo Santa Lucia hill Fig 1c)By contrast the presence of whitish carbonate-rich vein-lets cross-cutting the lava level in the peripheral areas(Electronic supplementary material ESM 1a freely avail-able online on the GSW website of the journal at httpeurjmingeoscienceworldorg) may be related to the intru-sion and crystallization of secondary carbonate mud in a

clear submarine environment beneath the carbonate plat-form as evident in the basal level of the volcanic outcrop atthe Acqua Palomba area Carbonate blocks percolated bybasaltic veinlets and micropods do also occur (ESM 1b)The submarine volcanic succession was cut by late dykespossibly related to the subaerial phase of the volcanoThese field data might help to clarify the nature of thevolcanic environment that has being alternatively consid-ered submarine or sub-aerial (eg Amore et al 1988Carveni et al 1991)

The lamprophyric dykes and hypabyssal rocks intrudedin the Adria block are from La Queglia ridge in theAbruzzi region and from Pietre Nere in the Apulian fore-land of the Italian region (eg Bellini 1957 De Fino et al1981 Durazzo et al 1984 Bigazzi et al 1996 Conticelliet al 2002 2007 Vichi et al 2005) The La Queglialamprophyre is intruded within Eocene reef limestonesradiometric dating of the rock provided unreliable datahence the age used in this paper is the maximum onereferred to the age of the intruded formation (eg Bellini1957 Durazzo et al 1984 Vichi et al 2004) The mela-syenite dyke of the Pietre Nere is part of a small intrusivemafic alkaline complex within the Paleocene reef lime-stones of the Gargano promontory in the Apulian region(eg De Fino et al 1981) Dating of these intrusive rocksgave a range from 58 to 65 Ma but the melasyenite studiedin this paper has an age of 622 Ma (Bigazzi et al 1996)Both the lamprophyric dyke and the melasyenite belong tothe Adria block a former portion of the African marginnow detached and isolated from the old continent

3 Sampling and analytical methods

Twenty-one samples from Pachino-Capo Passero volcaniccentre (Fig 1c) two samples from Pietre Nere and foursamples from La Queglia both from the Adria block werecollected The freshest samples among volcanic and sub-volcanic rocks and one reef-limestone from Capo Passerowere finely powdered in an agate mortar for chemicalanalyses In Table 1 the sampling locality latitude andlongitude petrography mineralogy and modal contentsfor the analysed samples are reported Whole-rock major-and trace-elements data (Tables 2 and 3) were acquired atActivation Laboratories (Ancaster ON Canada) viaFusion ICP-OES and ICP-MS respectively Lead wasanalysed by liquid ICP-MS for a better precision andaccuracy at low contents Analytical details can be foundon the website httpwwwactlabscom

Major-element compositions of minerals from five(ESM 2) samples were analysed by JEOL JXA-8600 elec-tron microprobe at CNR-IGG in Florence equipped withfour wave-length-dispersion spectrometers and integratedwith an energy-dispersion spectrometry system Operationconditions were 15 kV accelerating voltage and 10 nAbeam current Spot size is 1 mm Different times forelement collection were applied to the minerals Furtherdetails can be found in Vaggelli et al (1999)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 75

Tab

le1

L

ist

of

the

sam

ple

sst

ud

ied

wit

hre

po

rted

sam

pli

ng

loca

liti

es

coo

rdin

ates

m

iner

alo

gy

p

etro

gra

ph

yan

dm

od

alco

mp

osi

tio

n

Sam

ple

Lo

cali

tyL

atit

ud

eL

on

git

ud

eS

etti

ng

Ag

eR

ock

typ

eg

rou

pT

extu

reM

iner

alo

gy

and

mo

de

PA

C5

Ho

tel

Vit

tori

oN

36 4

00 7

100

E1

5 0

80 1

800

Dy

ke

70

7T

eph

rite

alk

alin

eA

ph

yri

ccp

x(0

6)thorn

op

q(0

2)

plg

olv

PA

C8

Ho

tel

Vit

tori

oN

36 4

10 7

500

E1

5 0

80 2

700

Dy

ke

70

7H

awai

ite

alk

alin

eH

p

orp

hy

riti

c(P

Ifrac14

26

)p

lg(2

12

)thorn

olv

(33

)thorn

cpx(1

0)thorn

op

q(0

2)

PA

C 14

Acq

ua

Pal

om

ba

N3

6 4

10 7

400

E1

5 0

70 7

500

Su

bae

rial

lav

a7

07

Bas

anit

eal

kal

ine

H

po

rphy

riti

c(P

Ifrac14

21

)o

lv(1

51

)thorn

cpx(2

7)thorn

op

q(2

6)thorn

plg

(04

)

PA

C 15

Pan

tan

oM

arg

her

ita

N3

6 4

20 5

600

E1

5 0

60 8

300

Su

bae

rial

lav

a7

07

Bas

anit

eal

kal

ine

Po

rph

yri

tic

(PIfrac14

15

)o

lv(1

16

)thorn

cpx(1

6)thorn

op

q(1

0)thorn

plg

(02

)

PA

C 18

So

uth

-Wes

to

fP

ach

ino

Vil

lag

e

N3

6 4

20 2

000

E1

5 0

50 1

200

Su

bae

rial

lav

a7

07

Tep

hri

teal

kal

ine

W

po

rph

yri

tic

(PIfrac14

7)

plg

(56

)thorn

op

q(0

1)

olv

PA

C1

Cap

oP

asse

roN

36 4

00 7

500

E1

5 0

80 1

700

Su

bm

arin

ela

va

70

7A

lkal

ib

asal

tm

ild

lyal

kal

ine

Po

rph

yri

tic

(PIfrac14

8)

cpx(4

3)thorn

olv

(25

)thorn

op

q(0

8)

plg

PA

C2

Cap

oP

asse

roN

36 4

00 7

500

E1

5 0

80 1

700

Su

bm

arin

ela

va

70

7A

lkal

ib

asal

tm

ild

lyal

kal

ine

Po

rph

yri

tic

(PIfrac14

19

)o

lv(1

01

)thorn

cpx(9

0)thorn

op

q(0

2)

plg

PA

C3

Cap

oP

asse

roN

36 4

00 7

500

E1

5 0

80 1

700

Su

bm

arin

ela

va

70

7A

lkal

ib

asal

tm

ild

lyal

kal

ine

Po

rph

yri

tic

(PIfrac14

13

)o

lv(7

8)thorn

cpx(5

1)thorn

op

q(0

1)

plg

PA

C9

Ho

tel

Vit

tori

oN

36 4

10 7

500

E1

5 0

80 2

700

Lo

ose

lav

ab

lock

70

7H

awai

ite

mil

dly

alk

alin

eH

p

orp

hy

riti

c(P

Ifrac14

29

)cp

x(1

48

)thorn

olv

(13

3)thorn

op

q(0

6)

plgthorn

gla

ssthorn

cal

PA

C 12

Acq

ua

Pal

om

ba

N3

6 4

10 7

400

E1

5 0

70 7

500

Su

bae

rial

lav

a7

07

Pic

rob

asal

tm

ild

lyal

kal

ine

H

po

rphy

riti

c(P

Ifrac14

50

)o

lv(2

28

)thorn

cpx(1

54

)thorn

plg

(10

2)thorn

op

q(1

7)

PA

C 16

So

uth

-Wes

to

fP

ach

ino

Vil

lag

e

N3

6 4

10 4

600

E1

5 0

50 1

500

Su

bae

rial

lav

a7

07

Pic

rob

asal

tm

ild

lyal

kal

ine

H

po

rphy

riti

c(P

Ifrac14

23

)o

lv(1

48

)thorn

cpx(7

1)thorn

plg

(11

)

op

q

PA

C 17

So

uth

-Wes

to

fP

ach

ino

Vil

lag

e

N3

6 4

10 5

900

E1

5 0

50 1

000

Su

bae

rial

lav

a7

07

Pic

rob

asal

tm

ild

lyal

kal

ine

H

po

rphy

riti

c(P

Ifrac14

30

)o

lv(1

30

)thorn

cpx(1

01

)thorn

plg

(64

)

op

q

PA

C 19

Co

zzo

San

taL

uci

aH

ill

N3

6 4

20 2

000

E1

5 0

60 2

000

Su

bae

rial

lav

a7

07

Pic

rob

asal

tm

ild

lyal

kal

ine

H

po

rphy

riti

c(P

Ifrac14

50

)o

lv(2

99

)thorn

cpx

(17

1)thorn

plg

(32

)thorn

op

q(0

1)

PA

C 21

Co

zzo

San

taL

uci

aH

ill

N3

6 4

20 2

600

E1

5 0

60 2

700

Red

dis

hla

va

70

7A

lkal

ib

asal

tm

ild

lyal

kal

ine

Po

rph

yri

tic

(PIfrac14

18

)o

lv(1

49

)thorn

cpx(1

3)thorn

op

q(1

4)thorn

plg

(03

)

PA

C4

Cap

oP

asse

roN

36 4

00 7

500

E1

5 0

80 1

700

Lim

esto

ne

ndashL

imes

ton

endash

ndashN

PM 15

Pu

nta

leP

ietr

eN

ere

N4

1 5

50 0

400

E1

5 2

00 2

500

Dy

ke

62

2m

ela-

syen

ite

Inte

rser

tal

K-f

eldthorn

ph

lthorn

cpxthorn

hb

lthorn

op

qthorn

sphthorn

apa

cal

NP

M 17

Pu

nta

leP

ietr

eN

ere

N4

1 5

50 0

200

E1

5 2

00 2

300

Dy

ke

62

2M

ela-

syen

ite

Inte

rser

tal

K-f

eldthorn

ph

lthorn

cpxthorn

hb

lthorn

op

qthorn

sphthorn

apa

cal

NP

M 13

Mo

nte

La

Qu

egli

aN

44 4

20 5

400

E1

3 5

20 2

000

Dy

ke

40

Lam

pro

ph

yre

Inte

rser

tal

ph

lthorncp

xthorn

olvthorn

op

qthorn

apathorn

melthorn

prwthorn

cal

NP

M2

Mo

nte

La

Qu

egli

aN

44 4

20 5

400

E1

3 5

20 2

000

Dy

ke

40

Lam

pro

ph

yre

Inte

rser

tal

ph

lthorncp

xthorn

olvthorn

op

qthorn

apathorn

melthorn

prwthorn

cal

NP

M3

Mo

nte

La

Qu

egli

aN

44 4

20 5

400

E1

3 5

20 2

000

Dy

ke

40

Lam

pro

ph

yre

Inte

rser

tal

ph

lthorncp

xthorn

olvthorn

op

qthorn

apathorn

melthorn

prwthorn

cal

NP

M5

Mo

nte

La

Qu

egli

aN

44 4

20 5

400

E1

3 5

20 2

000

Dy

ke

40

Lam

pro

ph

yre

Inte

rser

tal

ph

lthorncp

xthorn

olvthorn

op

qthorn

apathorn

melthorn

prwthorn

cal

Inb

rack

ets

are

rep

ort

edth

ev

ol

of

the

pre

ced

ing

min

eral

p

hen

ocr

yst

sar

ein

bo

ldw

her

eas

seco

nd

ary

min

eral

sin

ital

ic

Ww

eak

ly

Hh

igh

ly

PI

po

rph

yri

tic

ind

ex

plg

p

lag

iocl

ase

op

q

op

aqu

es

olv

o

liv

ine

cpx

cl

ino

py

rox

ene

K-f

eld

p

ota

ssiu

mfe

ldsp

ar

ph

lp

hlo

go

pit

eh

bl

amp

hib

ole

sp

hti

tan

ite

apa

apat

ite

mel

m

elil

ite

prv

p

ero

vsk

ite

cal

calc

ite

Ag

ere

po

rted

inm

illi

on

yea

rsaf

ter

Bar

ber

iet

al

(19

74

)an

dB

igaz

ziet

al

(19

96

)ag

esfo

rL

aQ

ueg

lia

dy

ke

are

esti

mat

esaf

ter

Bia

nch

ini

eta

l(2

00

8)

76 R Avanzinelli GT Sapienza S Conticelli

Tab

le2

M

ajo

r(w

t)

and

trac

eel

emen

ts(p

pm

)fo

rsa

mp

les

fro

mC

reta

ceo

us

Pac

hin

ondash

Cap

oP

asse

rov

olc

ano

Sam

ple

P

AC

5P

AC

8P

AC

14

PA

C1

5P

AC

18

PA

C1

PA

C2

PA

C3

PA

C9

PA

C1

6P

AC

17

PA

C1

9P

AC

21

PA

C4

Gro

up

a

lka

lka

lka

lka

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkli

mst

SiO

24

46

34

73

04

30

24

28

24

37

34

75

64

58

84

67

14

87

34

32

74

46

14

49

44

51

50

12

TiO

23

43

33

52

03

17

13

20

83

32

43

09

82

74

72

87

33

51

72

62

82

71

82

06

22

72

9

00

01

Al 2

O3

15

67

15

90

11

87

12

34

14

98

14

18

13

17

13

28

14

96

11

22

11

95

92

61

21

90

03

Fe 2

O3

12

09

11

59

13

82

13

62

12

42

12

49

12

58

12

61

11

17

13

62

13

41

13

20

13

59

00

7F

eOndash

ndashndash

ndashndash

ndashndash

ndashndash

ndashndash

ndashndash

ndashM

nO

01

57

01

61

01

71

01

69

01

70

01

36

01

57

01

53

01

67

01

62

01

68

01

66

01

68

00

14

Mg

O4

88

32

51

15

01

09

76

81

53

39

37

92

45

18

13

68

12

09

17

48

11

56

03

2C

aO1

05

58

47

11

24

11

02

11

25

10

05

99

09

95

10

44

10

69

10

72

96

01

09

45

63

8N

a 2O

33

13

96

29

12

88

30

93

26

27

92

83

38

21

73

20

21

68

25

40

08

K2O

13

81

49

09

40

86

10

81

31

09

70

91

14

90

61

07

30

54

08

0

00

1P

2O

50

82

07

80

57

05

30

62

05

20

48

04

80

56

03

80

41

03

20

41

0

01

LO

I1

91

27

70

77

12

42

91

17

41

06

09

50

32

18

81

28

11

70

45

43

64

Su

m9

88

39

91

99

99

89

96

61

00

38

99

68

99

10

99

99

10

03

59

98

71

00

11

10

04

21

00

53

10

06

5M

g-

48

47

39

52

65

98

65

24

56

10

49

86

63

45

63

07

51

94

70

07

67

76

75

53

66

47

91

42

Sc

14

21

25

27

17

23

24

23

24

28

30

30

26

1

Be

32

22

22

22

22

21

2

1V

25

93

34

29

53

19

28

72

44

24

82

44

26

72

75

27

12

12

27

16

Cr

60

40

26

02

20

2

02

30

24

02

30

30

36

03

10

56

02

80

2

0C

o3

82

34

74

52

74

44

14

42

55

15

95

54

4

1N

i

20

60

21

01

90

90

19

01

70

19

03

02

70

25

03

30

22

0

20

Cu

40

60

60

50

40

50

50

50

90

50

60

30

50

10

Zn

16

01

20

11

01

00

11

01

10

10

01

10

80

10

01

20

90

90

3

0G

a2

82

31

81

72

01

91

81

91

81

61

81

31

7

1G

e1

41

31

21

21

31

31

21

31

21

31

41

21

1

05

Rb

27

02

69

96

15

01

80

25

01

74

16

03

00

13

01

40

11

41

45

1

Sr

73

16

89

63

95

75

70

25

58

54

65

58

59

54

26

45

43

23

53

31

33

Y3

28

31

82

41

24

82

73

23

42

24

23

42

39

20

52

27

16

82

04

16

Zr

33

22

74

21

62

15

24

41

99

20

61

99

19

81

61

17

31

39

15

9

4N

b6

33

53

94

10

34

03

99

31

73

07

31

74

57

27

02

75

20

42

66

06

0S

b0

71

20

51

41

00

60

40

6

02

15

0

21

90

6

02

Cs

05

05

03

02

02

01

02

01

07

02

0

1

01

02

0

1B

a3

73

39

02

82

22

52

81

21

02

06

21

03

74

17

31

68

12

81

95

7L

a5

45

37

53

52

30

33

37

27

92

87

27

96

19

22

22

60

17

92

34

07

Ce

11

67

67

71

56

37

70

05

78

59

25

78

11

34

71

53

43

83

48

70

6

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 77

All the samples selected for major and trace elementanalysis with the sole exception of the weathered PAC 18were also analyzed for Sr and Pb isotopes at the RadiogenicIsotopes Laboratory of the University of Firenze Nd iso-tope analyses were performed on a selection of five sam-ples Limestone sample PAC04 at the contact with lavaflow was also analysed for Sr isotopes In order to provide auseful comparison we also measured volcanic rockserupted within the Central Mediterranean from the sub-volcanic rocks found within the Apulian foreland whichrepresent the magmatic events closest in time to thePachino-Capo Passero rock in the area and fill the time-gap between Pachino-Capo Passero Cretaceous productsand the Neogene Hyblean Plateau magmas

All the samples with exclusion of the limestone wereleached in 1 N HCl and dried on a hot-plate at T70 C toleach out possible contamination with carbonate or sea-water All samples were processed by sequential HF-HNO3-HCl dissolution and the Sr Nd and Pb fractionswere purified and collected as described in Avanzinelliet al (2005) Sr-Nd-Pb isotope data were obtained usinga Thermal Ionisation Mass Spectrometer (TIMS)ThermoFinnigan Triton-Ti During period of measure-ment the mean value for 87Sr86Sr of the NIST SRM 987standard was 0710249 12 (2s n frac14 29) and the meanvalues for 143Nd144Nd of the NdFi and La Jolla standardswere 05114685 (2s nfrac14 33) and 0511846 7 (2s nfrac1467) respectively Pb isotope ratios were corrected usingreplicate analyses of NIST SRM 981 standard The within-run averages for 206Pb204Pb 207Pb204Pb and 208Pb204Pbwere 16891 5 15427 7 and 36505 21 (2s nfrac14 5)respectively long-term reproducibility for the same ratiosyielded the following values 16888 8 15424 9 and36495 27 (2s n frac14 102) respectively An averagefractionation factor of 0149 per mass unit relative tothe reference values of Thirlwall (2000) was applied to allPb isotope ratios The accuracy of Pb isotope data wasfurther tested by replicate measurements of AGV-1 yield-ing averages of 206Pb204Pb 18940 0014 (2s n frac14 11)207Pb204Pb 15653 0017 (2s n frac14 11) 208Pb204Pb38566 0061 (2s n frac14 11) which are within error ofthe values reported by Weis et al (2006) Analytical detailsare provided in Avanzinelli et al (2005) All data alongwith standard reproducibility are reported in Tables 4 and5 internal errors have been fully propagated to account forthe added imprecision due to age correction

4 Petrography and classification

The Pachino-Capo Passero outcrops represent a formersmall volcanic island characterised by submarine to sub-aerial volcanic products Submarine lavas are charac-terised by brecciation with jigsaw fit texture filled up byaltered hyaloclastic glass or secondary carbonate material(ESM 1a) The freshest samples show porphyritic to glo-meroporphyritic textures (Porphyritic Index hereafter PIfrac14 8ndash19 ESM 3) Phenocrysts are made of olivine zonedT

able

2

Co

nti

nu

ed

Sam

ple

P

AC

5P

AC

8P

AC

14

PA

C1

5P

AC

18

PA

C1

PA

C2

PA

C3

PA

C9

PA

C1

6P

AC

17

PA

C1

9P

AC

21

PA

C4

Gro

up

a

lka

lka

lka

lka

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkli

mst

Pr

13

69

44

88

47

88

87

77

27

26

72

01

22

59

86

93

49

16

08

01

2N

d5

64

41

03

86

34

93

84

31

23

17

31

24

70

26

43

00

21

82

65

05

9S

m1

11

87

07

79

73

38

09

67

67

00

67

68

42

58

26

44

50

26

05

01

5E

u3

76

30

52

74

25

72

82

24

12

40

24

12

63

20

42

24

17

12

11

00

8G

d9

04

78

97

00

65

67

25

60

16

08

60

16

40

53

45

98

43

65

26

02

0T

b1

41

12

71

09

10

91

15

09

60

99

09

60

93

08

50

93

07

20

90

00

3D

y7

18

70

05

60

56

06

01

51

15

33

51

15

06

44

45

02

38

54

83

02

0H

o1

19

12

70

92

09

61

03

08

90

90

08

90

90

07

20

89

06

50

81

00

4E

r3

04

31

52

25

25

02

72

22

42

27

22

42

41

18

42

30

16

82

04

01

2T

m0

38

20

41

80

29

70

33

40

34

90

29

40

29

10

29

40

33

60

25

70

30

00

22

40

27

30

01

5Y

b2

16

25

11

66

19

52

06

17

21

70

17

22

03

15

11

74

12

71

58

01

0L

u0

27

40

35

50

21

50

25

30

28

00

23

60

23

80

23

60

29

00

19

80

24

00

17

90

21

30

01

5H

f8

06

65

65

36

05

05

15

04

34

14

93

64

2

01

Ta

48

53

35

32

62

79

32

32

43

25

22

43

27

32

07

22

01

67

21

8

00

1P

b3

82

31

72

32

95

81

74

88

61

51

50

91

2

05

Th

55

05

58

33

52

78

33

94

30

26

42

70

81

72

11

23

11

76

22

6

00

5U

18

21

98

11

40

93

11

81

42

08

90

76

26

40

76

06

90

58

07

81

47

alk

al

kal

ine

m

alk

m

ild

lyal

kal

ine

Mg

-

[Mg

(M

gthorn

08

5

Fe2thorn

)

78 R Avanzinelli GT Sapienza S Conticelli

clinopyroxene and subordinate opaques set in a micro-crystalline groundmass made up of dominant plagioclaseand subordinate olivine clinopyroxene and opaque miner-als The strongly altered samples display serpentine afterolivine with altered clinopyroxene and groundmass andabundant secondary calcite Two dykes intruding the

submarine sequence of lava flows have been found theyhave fairly different petrographic characteristics from por-phyriticglomeroporphyritic (PAC 8 PI frac14 25 ESM 3)to almost aphyric textures (PAC 5 ESM 3) The porphyri-ticglomeroporphyritic dyke shows phenocrysts of freshplagioclase iddingsitised olivine and rare clinopyroxene

Table 3 Major (wt) and trace elements (ppm) for selected samples from La Queglia and Pietre Nere dykes

Sample NPM 15 NPM 17 NPM 13 NPM 2 NPM 3 NPM 5Group PN PN LQ LQ LQ LQ

SiO2 3954 4019 3645 3581 3557 3571TiO2 4946 333 352 351 3889 3835Al2O3 1092 1074 1135 934 1026 1087Fe2O3 591 617 754 726 1167 1132FeO 875 758 389 329 ndash ndashMnO 0180 013 012 016 0187 0181MgO 666 827 1394 1688 1582 1465CaO 1094 1396 1026 1302 918 979Na2O 169 157 074 049 057 069K2O 495 418 140 081 145 131P2O5 137 095 145 113 147 146LOI 387 284 889 816 952 882Sum 9972 9990 9955 9984 9959 9864Mg- 8842 7576 8116 8442 8542 8742Sc 20 ndash 300 365 19 16Be ndash ndash ndash ndash ndash ndashV 352 281 391 389 350 381Cr 90 170 311 388 300 220Co 42 386 460 511 46 43Ni 70 954 177 233 170 140Cu 70 ndash ndash ndash 60 60Zn 140 ndash ndash ndash 110 110Ga 24 ndash ndash ndash 20 20Ge 2 ndash ndash ndash 1 1Rb 92 51 44 28 38 35Sr 814 673 1560 988 1869 2665Y 32 30 18 26 30 30Zr 498 372 475 393 404 403Nb 126 96 142 130 121 123Sb 05 ndash ndash ndash 05 05Cs 12 ndash ndash ndash 05 05Ba 1292 1062 1140 1140 1185 1124La 102 751 730 815 872 811Ce 203 1464 950 1317 148 132Pr 230 ndash ndash 133 156 140Nd 909 687 43 591 601 541Sm 161 129 758 115 116 104Eu 449 387 286 364 333 305Gd 143 ndash ndash 116 111 102Tb 16 146 105 133 13 13Dy 72 ndash ndash 723 62 60Ho 12 ndash ndash 115 10 10Er 28 ndash ndash 295 26 25Tm 034 ndash ndash 037 033 032Yb 19 187 207 210 19 19Lu 027 026 028 029 027 027Hf 104 1171 115 117 81 74Ta 81 745 450 461 58 52Pb 60 48 60 75 75 90Th 108 87 51 91 85 67U 35 285 31 33 36 33

LQ La Queglia PN Pietre Nere Mg- [Mg(Mgthorn085Fe2thorn)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 79

with accessory opaques set in a microcrystalline intersertalgroundmass The aphyric dyke shows rare clinopyroxenephenocrysts set in a micro- to cryptocrystalline trachyticgroundmass made of plagioclase clinopyroxene olivineand opaques

Subaerial lava flows overlying Rudist-bearing carbonatesmade up a small lava plateau in the peripheral sectors of thevolcanic area whereas close to the village of Pachino in thecentral sector of the volcanic area (Fig 1c) blocky lavas andminor reddish scoriae are piled up to form a gentle hill (ieCozzo Santa Lucia hill Fig 1c) which might have been thesite of a possible subaerial erupting centre Two types ofsubaerial lava flows are found in term of petrographic char-acteristics the mildly porphyritic and the melanocratic onesThe former have porphyritic to glomeroporphyritic textureswith phenocrysts of olivine clinopyroxene minor opaquesand rare plagioclase (Samples PAC 13ndash15 Table 1 ESM 3)set in a microcrystalline groundmass consisting of the samephases of the phenocryst population Melanocratic lava flowsshow highly porphyritic textures (PAC 16ndash17 and 19ndash21 PIfrac14 18ndash50 ESM 3) with abundant olivine and clinopyroxenephenocrysts beside minor opaques and plagioclase set in anintergranular groundmass Olivine shows incipient iddingsi-tisation Some melanocratic lava samples (ie PAC 19) havethe highest porphyritic index associated to the coarsest grainsize (ESM 3) In these lavas olivine and clinopyroxene arethe most abundant phenocrysts with subordinate plagioclaseRare glomeroporphiric aggregates made of plagioclase andclinopyroxene also occur Reddish scoriae are highly vesi-culated with aphyric to glassy textures Rare small-sized

plagioclase crystals are the sole phenocrysts which are dis-persed in a glassy to trachytic groundmass Some iddingsi-tised olivine crystals also occur in the groundmass

The La Queglia dyke shows an intersertal holocrystal-line texture with skeletal to elongated olivine crystalsbeside abundant phlogopite and clinopyroxene minoramphibole K-feldspar and opaques and accessoryamounts of perovskite and apatite Variable amount ofcalcite of debatable nature is also found (Vichi et al2004) The Pietre Nere melasyenitic dyke (De Fino et al1981) has an intersertal holocrystalline texture with abun-dant K-feldspar clinopyroxene biotite and amphibole asprimary phases with accessory titanite and apatite andcalcite among the secondary phases

From a chemical point of view the studied samples areclassified according to the total alkali-silica diagram (TASFig 2 Le Bas et al 1986) two groups might be distin-guished within the Pachino ndash Capo Passero samples on thebasis of different enrichment in alkali defining twoslightly distinct differentiation trends The two groups aredefined hereafter as Na-alkaline and a mildly alkaline andwill be used in the following discussion

Volcanic rocks belonging to the alkaline group range incompositions from basanite to hawaiite passing throughtephrite (Fig 2) This group includes the dykes and twoperipheral lava flows (ie PAC 14 and PAC 15) samplePAC 18 also belongs to the alkaline group although itpresents clear evidence of weathering The lavas of themildly alkaline group range in composition from picroba-salt to alkali basalt with the most differentiated sample

Table 4 Sr-Nd isotope data of Pachino ndash Capo Passero Upper Cretaceous volcanic rocks Pietre Nere melasyenite La Queglia lamprophyre

Age Rb Sr Nd Sm 87Sr86Sr 87Sr86Sr 143Nd144Nd 143Nd144NdMa ppm ppm ppm ppm measured 2 se initial 2 se measured 2 se initial 2 se

Pachino-Capo PasseroPAC 05 707 2 270 731 564 111 0703502 0000006 0703395 0000010 ndash ndash ndashPAC 08 707 2 269 689 410 870 0703244 0000006 0703130 0000011 0512921 0000005 0512862 0000006PAC 14 707 2 960 639 386 779 0703172 0000006 0703128 0000007 0512883 0000005 0512827 0000007PAC 15 707 2 150 575 349 733 0703151 0000006 0703075 0000008 ndash ndash ndashPAC 01 707 2 250 579 462 941 0703174 0000006 0703049 0000012 ndash ndash ndashPAC 02 707 2 174 546 317 700 0703357 0000006 0703265 0000010 0512894 0000005 0512833 0000007PAC 03 707 2 160 558 312 676 0703375 0000006 0703291 0000009 ndash ndash ndashPAC 09 707 2 300 595 470 842 0703386 0000006 0703240 0000013 ndash ndash ndashPAC 16 707 2 130 426 264 582 0703299 0000008 0703210 0000010 ndash ndash ndashPAC 17 707 2 140 454 300 644 0703013 0000006 0702924 0000009 ndash ndash ndashPAC 19 707 2 114 323 218 502 0703168 0000006 0703066 0000010 0512902 0000005 0512837 0000007PAC 21 707 2 145 533 265 605 0703504 0000005 0703425 0000008 0512884 0000004 0512821 0000006PAC 04 707 2 1 133 059 015 0707267 0000006 0707245 0000006 ndash ndash ndash

Pietre Nere foiditeNPM 15 622 08 92 814 909 161 0704058 0000006 0703769 0000023 0512830 0000007 0512786 0000008NPM 17 622 08 51 673 687 129 0704070 0000007 0703877 0000016 0512752 0000004 0512706 0000005

Mt La Queglia lamprophyreNPM 13 40 44 1560 430 758 0703440 0000009 0703394 0000010 0512891 0000006 0512863 0000006NPM 2 40 28 988 591 115 0703429 0000006 0703383 0000007 0512930 0000004 0512899 0000005NPM 3 40 38 1869 601 116 0703762 0000007 0703728 0000007 ndash ndash ndashNPM 5 40 35 2665 541 104 0703584 0000005 0703562 0000005 ndash ndash ndash

Ages after Barberi et al (1974) and Bigazzi et al (1996) ages for La Queglia dyke are estimates after Bianchini et al (2008) NPM 13 andNPM 15 data are from Conticelli et al (2007) Standard errors (2 se) on initial isotope ratios are propagated through a Monte-Carlosimulation assuming 5 error on Rb Sr Sm and Nd concentrations

80 R Avanzinelli GT Sapienza S Conticelli

Tab

le2

M

ajo

r(w

t)

and

trac

eel

emen

ts(p

pm

)fo

rsa

mp

les

fro

mC

reta

ceo

us

Pac

hin

ondash

Cap

oP

asse

rov

olc

ano

Sam

ple

P

AC

5P

AC

8P

AC

14

PA

C1

5P

AC

18

PA

C1

PA

C2

PA

C3

PA

C9

PA

C1

6P

AC

17

PA

C1

9P

AC

21

PA

C4

Gro

up

a

lka

lka

lka

lka

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkli

mst

SiO

24

46

34

73

04

30

24

28

24

37

34

75

64

58

84

67

14

87

34

32

74

46

14

49

44

51

50

12

TiO

23

43

33

52

03

17

13

20

83

32

43

09

82

74

72

87

33

51

72

62

82

71

82

06

22

72

9

00

01

Al 2

O3

15

67

15

90

11

87

12

34

14

98

14

18

13

17

13

28

14

96

11

22

11

95

92

61

21

90

03

Fe 2

O3

12

09

11

59

13

82

13

62

12

42

12

49

12

58

12

61

11

17

13

62

13

41

13

20

13

59

00

7F

eOndash

ndashndash

ndashndash

ndashndash

ndashndash

ndashndash

ndashndash

ndashM

nO

01

57

01

61

01

71

01

69

01

70

01

36

01

57

01

53

01

67

01

62

01

68

01

66

01

68

00

14

Mg

O4

88

32

51

15

01

09

76

81

53

39

37

92

45

18

13

68

12

09

17

48

11

56

03

2C

aO1

05

58

47

11

24

11

02

11

25

10

05

99

09

95

10

44

10

69

10

72

96

01

09

45

63

8N

a 2O

33

13

96

29

12

88

30

93

26

27

92

83

38

21

73

20

21

68

25

40

08

K2O

13

81

49

09

40

86

10

81

31

09

70

91

14

90

61

07

30

54

08

0

00

1P

2O

50

82

07

80

57

05

30

62

05

20

48

04

80

56

03

80

41

03

20

41

0

01

LO

I1

91

27

70

77

12

42

91

17

41

06

09

50

32

18

81

28

11

70

45

43

64

Su

m9

88

39

91

99

99

89

96

61

00

38

99

68

99

10

99

99

10

03

59

98

71

00

11

10

04

21

00

53

10

06

5M

g-

48

47

39

52

65

98

65

24

56

10

49

86

63

45

63

07

51

94

70

07

67

76

75

53

66

47

91

42

Sc

14

21

25

27

17

23

24

23

24

28

30

30

26

1

Be

32

22

22

22

22

21

2

1V

25

93

34

29

53

19

28

72

44

24

82

44

26

72

75

27

12

12

27

16

Cr

60

40

26

02

20

2

02

30

24

02

30

30

36

03

10

56

02

80

2

0C

o3

82

34

74

52

74

44

14

42

55

15

95

54

4

1N

i

20

60

21

01

90

90

19

01

70

19

03

02

70

25

03

30

22

0

20

Cu

40

60

60

50

40

50

50

50

90

50

60

30

50

10

Zn

16

01

20

11

01

00

11

01

10

10

01

10

80

10

01

20

90

90

3

0G

a2

82

31

81

72

01

91

81

91

81

61

81

31

7

1G

e1

41

31

21

21

31

31

21

31

21

31

41

21

1

05

Rb

27

02

69

96

15

01

80

25

01

74

16

03

00

13

01

40

11

41

45

1

Sr

73

16

89

63

95

75

70

25

58

54

65

58

59

54

26

45

43

23

53

31

33

Y3

28

31

82

41

24

82

73

23

42

24

23

42

39

20

52

27

16

82

04

16

Zr

33

22

74

21

62

15

24

41

99

20

61

99

19

81

61

17

31

39

15

9

4N

b6

33

53

94

10

34

03

99

31

73

07

31

74

57

27

02

75

20

42

66

06

0S

b0

71

20

51

41

00

60

40

6

02

15

0

21

90

6

02

Cs

05

05

03

02

02

01

02

01

07

02

0

1

01

02

0

1B

a3

73

39

02

82

22

52

81

21

02

06

21

03

74

17

31

68

12

81

95

7L

a5

45

37

53

52

30

33

37

27

92

87

27

96

19

22

22

60

17

92

34

07

Ce

11

67

67

71

56

37

70

05

78

59

25

78

11

34

71

53

43

83

48

70

6

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 77

All the samples selected for major and trace elementanalysis with the sole exception of the weathered PAC 18were also analyzed for Sr and Pb isotopes at the RadiogenicIsotopes Laboratory of the University of Firenze Nd iso-tope analyses were performed on a selection of five sam-ples Limestone sample PAC04 at the contact with lavaflow was also analysed for Sr isotopes In order to provide auseful comparison we also measured volcanic rockserupted within the Central Mediterranean from the sub-volcanic rocks found within the Apulian foreland whichrepresent the magmatic events closest in time to thePachino-Capo Passero rock in the area and fill the time-gap between Pachino-Capo Passero Cretaceous productsand the Neogene Hyblean Plateau magmas

All the samples with exclusion of the limestone wereleached in 1 N HCl and dried on a hot-plate at T70 C toleach out possible contamination with carbonate or sea-water All samples were processed by sequential HF-HNO3-HCl dissolution and the Sr Nd and Pb fractionswere purified and collected as described in Avanzinelliet al (2005) Sr-Nd-Pb isotope data were obtained usinga Thermal Ionisation Mass Spectrometer (TIMS)ThermoFinnigan Triton-Ti During period of measure-ment the mean value for 87Sr86Sr of the NIST SRM 987standard was 0710249 12 (2s n frac14 29) and the meanvalues for 143Nd144Nd of the NdFi and La Jolla standardswere 05114685 (2s nfrac14 33) and 0511846 7 (2s nfrac1467) respectively Pb isotope ratios were corrected usingreplicate analyses of NIST SRM 981 standard The within-run averages for 206Pb204Pb 207Pb204Pb and 208Pb204Pbwere 16891 5 15427 7 and 36505 21 (2s nfrac14 5)respectively long-term reproducibility for the same ratiosyielded the following values 16888 8 15424 9 and36495 27 (2s n frac14 102) respectively An averagefractionation factor of 0149 per mass unit relative tothe reference values of Thirlwall (2000) was applied to allPb isotope ratios The accuracy of Pb isotope data wasfurther tested by replicate measurements of AGV-1 yield-ing averages of 206Pb204Pb 18940 0014 (2s n frac14 11)207Pb204Pb 15653 0017 (2s n frac14 11) 208Pb204Pb38566 0061 (2s n frac14 11) which are within error ofthe values reported by Weis et al (2006) Analytical detailsare provided in Avanzinelli et al (2005) All data alongwith standard reproducibility are reported in Tables 4 and5 internal errors have been fully propagated to account forthe added imprecision due to age correction

4 Petrography and classification

The Pachino-Capo Passero outcrops represent a formersmall volcanic island characterised by submarine to sub-aerial volcanic products Submarine lavas are charac-terised by brecciation with jigsaw fit texture filled up byaltered hyaloclastic glass or secondary carbonate material(ESM 1a) The freshest samples show porphyritic to glo-meroporphyritic textures (Porphyritic Index hereafter PIfrac14 8ndash19 ESM 3) Phenocrysts are made of olivine zonedT

able

2

Co

nti

nu

ed

Sam

ple

P

AC

5P

AC

8P

AC

14

PA

C1

5P

AC

18

PA

C1

PA

C2

PA

C3

PA

C9

PA

C1

6P

AC

17

PA

C1

9P

AC

21

PA

C4

Gro

up

a

lka

lka

lka

lka

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkm

a

lkli

mst

Pr

13

69

44

88

47

88

87

77

27

26

72

01

22

59

86

93

49

16

08

01

2N

d5

64

41

03

86

34

93

84

31

23

17

31

24

70

26

43

00

21

82

65

05

9S

m1

11

87

07

79

73

38

09

67

67

00

67

68

42

58

26

44

50

26

05

01

5E

u3

76

30

52

74

25

72

82

24

12

40

24

12

63

20

42

24

17

12

11

00

8G

d9

04

78

97

00

65

67

25

60

16

08

60

16

40

53

45

98

43

65

26

02

0T

b1

41

12

71

09

10

91

15

09

60

99

09

60

93

08

50

93

07

20

90

00

3D

y7

18

70

05

60

56

06

01

51

15

33

51

15

06

44

45

02

38

54

83

02

0H

o1

19

12

70

92

09

61

03

08

90

90

08

90

90

07

20

89

06

50

81

00

4E

r3

04

31

52

25

25

02

72

22

42

27

22

42

41

18

42

30

16

82

04

01

2T

m0

38

20

41

80

29

70

33

40

34

90

29

40

29

10

29

40

33

60

25

70

30

00

22

40

27

30

01

5Y

b2

16

25

11

66

19

52

06

17

21

70

17

22

03

15

11

74

12

71

58

01

0L

u0

27

40

35

50

21

50

25

30

28

00

23

60

23

80

23

60

29

00

19

80

24

00

17

90

21

30

01

5H

f8

06

65

65

36

05

05

15

04

34

14

93

64

2

01

Ta

48

53

35

32

62

79

32

32

43

25

22

43

27

32

07

22

01

67

21

8

00

1P

b3

82

31

72

32

95

81

74

88

61

51

50

91

2

05

Th

55

05

58

33

52

78

33

94

30

26

42

70

81

72

11

23

11

76

22

6

00

5U

18

21

98

11

40

93

11

81

42

08

90

76

26

40

76

06

90

58

07

81

47

alk

al

kal

ine

m

alk

m

ild

lyal

kal

ine

Mg

-

[Mg

(M

gthorn

08

5

Fe2thorn

)

78 R Avanzinelli GT Sapienza S Conticelli

clinopyroxene and subordinate opaques set in a micro-crystalline groundmass made up of dominant plagioclaseand subordinate olivine clinopyroxene and opaque miner-als The strongly altered samples display serpentine afterolivine with altered clinopyroxene and groundmass andabundant secondary calcite Two dykes intruding the

submarine sequence of lava flows have been found theyhave fairly different petrographic characteristics from por-phyriticglomeroporphyritic (PAC 8 PI frac14 25 ESM 3)to almost aphyric textures (PAC 5 ESM 3) The porphyri-ticglomeroporphyritic dyke shows phenocrysts of freshplagioclase iddingsitised olivine and rare clinopyroxene

Table 3 Major (wt) and trace elements (ppm) for selected samples from La Queglia and Pietre Nere dykes

Sample NPM 15 NPM 17 NPM 13 NPM 2 NPM 3 NPM 5Group PN PN LQ LQ LQ LQ

SiO2 3954 4019 3645 3581 3557 3571TiO2 4946 333 352 351 3889 3835Al2O3 1092 1074 1135 934 1026 1087Fe2O3 591 617 754 726 1167 1132FeO 875 758 389 329 ndash ndashMnO 0180 013 012 016 0187 0181MgO 666 827 1394 1688 1582 1465CaO 1094 1396 1026 1302 918 979Na2O 169 157 074 049 057 069K2O 495 418 140 081 145 131P2O5 137 095 145 113 147 146LOI 387 284 889 816 952 882Sum 9972 9990 9955 9984 9959 9864Mg- 8842 7576 8116 8442 8542 8742Sc 20 ndash 300 365 19 16Be ndash ndash ndash ndash ndash ndashV 352 281 391 389 350 381Cr 90 170 311 388 300 220Co 42 386 460 511 46 43Ni 70 954 177 233 170 140Cu 70 ndash ndash ndash 60 60Zn 140 ndash ndash ndash 110 110Ga 24 ndash ndash ndash 20 20Ge 2 ndash ndash ndash 1 1Rb 92 51 44 28 38 35Sr 814 673 1560 988 1869 2665Y 32 30 18 26 30 30Zr 498 372 475 393 404 403Nb 126 96 142 130 121 123Sb 05 ndash ndash ndash 05 05Cs 12 ndash ndash ndash 05 05Ba 1292 1062 1140 1140 1185 1124La 102 751 730 815 872 811Ce 203 1464 950 1317 148 132Pr 230 ndash ndash 133 156 140Nd 909 687 43 591 601 541Sm 161 129 758 115 116 104Eu 449 387 286 364 333 305Gd 143 ndash ndash 116 111 102Tb 16 146 105 133 13 13Dy 72 ndash ndash 723 62 60Ho 12 ndash ndash 115 10 10Er 28 ndash ndash 295 26 25Tm 034 ndash ndash 037 033 032Yb 19 187 207 210 19 19Lu 027 026 028 029 027 027Hf 104 1171 115 117 81 74Ta 81 745 450 461 58 52Pb 60 48 60 75 75 90Th 108 87 51 91 85 67U 35 285 31 33 36 33

LQ La Queglia PN Pietre Nere Mg- [Mg(Mgthorn085Fe2thorn)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 79

with accessory opaques set in a microcrystalline intersertalgroundmass The aphyric dyke shows rare clinopyroxenephenocrysts set in a micro- to cryptocrystalline trachyticgroundmass made of plagioclase clinopyroxene olivineand opaques

Subaerial lava flows overlying Rudist-bearing carbonatesmade up a small lava plateau in the peripheral sectors of thevolcanic area whereas close to the village of Pachino in thecentral sector of the volcanic area (Fig 1c) blocky lavas andminor reddish scoriae are piled up to form a gentle hill (ieCozzo Santa Lucia hill Fig 1c) which might have been thesite of a possible subaerial erupting centre Two types ofsubaerial lava flows are found in term of petrographic char-acteristics the mildly porphyritic and the melanocratic onesThe former have porphyritic to glomeroporphyritic textureswith phenocrysts of olivine clinopyroxene minor opaquesand rare plagioclase (Samples PAC 13ndash15 Table 1 ESM 3)set in a microcrystalline groundmass consisting of the samephases of the phenocryst population Melanocratic lava flowsshow highly porphyritic textures (PAC 16ndash17 and 19ndash21 PIfrac14 18ndash50 ESM 3) with abundant olivine and clinopyroxenephenocrysts beside minor opaques and plagioclase set in anintergranular groundmass Olivine shows incipient iddingsi-tisation Some melanocratic lava samples (ie PAC 19) havethe highest porphyritic index associated to the coarsest grainsize (ESM 3) In these lavas olivine and clinopyroxene arethe most abundant phenocrysts with subordinate plagioclaseRare glomeroporphiric aggregates made of plagioclase andclinopyroxene also occur Reddish scoriae are highly vesi-culated with aphyric to glassy textures Rare small-sized

plagioclase crystals are the sole phenocrysts which are dis-persed in a glassy to trachytic groundmass Some iddingsi-tised olivine crystals also occur in the groundmass

The La Queglia dyke shows an intersertal holocrystal-line texture with skeletal to elongated olivine crystalsbeside abundant phlogopite and clinopyroxene minoramphibole K-feldspar and opaques and accessoryamounts of perovskite and apatite Variable amount ofcalcite of debatable nature is also found (Vichi et al2004) The Pietre Nere melasyenitic dyke (De Fino et al1981) has an intersertal holocrystalline texture with abun-dant K-feldspar clinopyroxene biotite and amphibole asprimary phases with accessory titanite and apatite andcalcite among the secondary phases

From a chemical point of view the studied samples areclassified according to the total alkali-silica diagram (TASFig 2 Le Bas et al 1986) two groups might be distin-guished within the Pachino ndash Capo Passero samples on thebasis of different enrichment in alkali defining twoslightly distinct differentiation trends The two groups aredefined hereafter as Na-alkaline and a mildly alkaline andwill be used in the following discussion

Volcanic rocks belonging to the alkaline group range incompositions from basanite to hawaiite passing throughtephrite (Fig 2) This group includes the dykes and twoperipheral lava flows (ie PAC 14 and PAC 15) samplePAC 18 also belongs to the alkaline group although itpresents clear evidence of weathering The lavas of themildly alkaline group range in composition from picroba-salt to alkali basalt with the most differentiated sample

Table 4 Sr-Nd isotope data of Pachino ndash Capo Passero Upper Cretaceous volcanic rocks Pietre Nere melasyenite La Queglia lamprophyre

Age Rb Sr Nd Sm 87Sr86Sr 87Sr86Sr 143Nd144Nd 143Nd144NdMa ppm ppm ppm ppm measured 2 se initial 2 se measured 2 se initial 2 se

Pachino-Capo PasseroPAC 05 707 2 270 731 564 111 0703502 0000006 0703395 0000010 ndash ndash ndashPAC 08 707 2 269 689 410 870 0703244 0000006 0703130 0000011 0512921 0000005 0512862 0000006PAC 14 707 2 960 639 386 779 0703172 0000006 0703128 0000007 0512883 0000005 0512827 0000007PAC 15 707 2 150 575 349 733 0703151 0000006 0703075 0000008 ndash ndash ndashPAC 01 707 2 250 579 462 941 0703174 0000006 0703049 0000012 ndash ndash ndashPAC 02 707 2 174 546 317 700 0703357 0000006 0703265 0000010 0512894 0000005 0512833 0000007PAC 03 707 2 160 558 312 676 0703375 0000006 0703291 0000009 ndash ndash ndashPAC 09 707 2 300 595 470 842 0703386 0000006 0703240 0000013 ndash ndash ndashPAC 16 707 2 130 426 264 582 0703299 0000008 0703210 0000010 ndash ndash ndashPAC 17 707 2 140 454 300 644 0703013 0000006 0702924 0000009 ndash ndash ndashPAC 19 707 2 114 323 218 502 0703168 0000006 0703066 0000010 0512902 0000005 0512837 0000007PAC 21 707 2 145 533 265 605 0703504 0000005 0703425 0000008 0512884 0000004 0512821 0000006PAC 04 707 2 1 133 059 015 0707267 0000006 0707245 0000006 ndash ndash ndash

Pietre Nere foiditeNPM 15 622 08 92 814 909 161 0704058 0000006 0703769 0000023 0512830 0000007 0512786 0000008NPM 17 622 08 51 673 687 129 0704070 0000007 0703877 0000016 0512752 0000004 0512706 0000005

Mt La Queglia lamprophyreNPM 13 40 44 1560 430 758 0703440 0000009 0703394 0000010 0512891 0000006 0512863 0000006NPM 2 40 28 988 591 115 0703429 0000006 0703383 0000007 0512930 0000004 0512899 0000005NPM 3 40 38 1869 601 116 0703762 0000007 0703728 0000007 ndash ndash ndashNPM 5 40 35 2665 541 104 0703584 0000005 0703562 0000005 ndash ndash ndash

Ages after Barberi et al (1974) and Bigazzi et al (1996) ages for La Queglia dyke are estimates after Bianchini et al (2008) NPM 13 andNPM 15 data are from Conticelli et al (2007) Standard errors (2 se) on initial isotope ratios are propagated through a Monte-Carlosimulation assuming 5 error on Rb Sr Sm and Nd concentrations

80 R Avanzinelli GT Sapienza S Conticelli

All the samples selected for major and trace elementanalysis with the sole exception of the weathered PAC 18were also analyzed for Sr and Pb isotopes at the RadiogenicIsotopes Laboratory of the University of Firenze Nd iso-tope analyses were performed on a selection of five sam-ples Limestone sample PAC04 at the contact with lavaflow was also analysed for Sr isotopes In order to provide auseful comparison we also measured volcanic rockserupted within the Central Mediterranean from the sub-volcanic rocks found within the Apulian foreland whichrepresent the magmatic events closest in time to thePachino-Capo Passero rock in the area and fill the time-gap between Pachino-Capo Passero Cretaceous productsand the Neogene Hyblean Plateau magmas

All the samples with exclusion of the limestone wereleached in 1 N HCl and dried on a hot-plate at T70 C toleach out possible contamination with carbonate or sea-water All samples were processed by sequential HF-HNO3-HCl dissolution and the Sr Nd and Pb fractionswere purified and collected as described in Avanzinelliet al (2005) Sr-Nd-Pb isotope data were obtained usinga Thermal Ionisation Mass Spectrometer (TIMS)ThermoFinnigan Triton-Ti During period of measure-ment the mean value for 87Sr86Sr of the NIST SRM 987standard was 0710249 12 (2s n frac14 29) and the meanvalues for 143Nd144Nd of the NdFi and La Jolla standardswere 05114685 (2s nfrac14 33) and 0511846 7 (2s nfrac1467) respectively Pb isotope ratios were corrected usingreplicate analyses of NIST SRM 981 standard The within-run averages for 206Pb204Pb 207Pb204Pb and 208Pb204Pbwere 16891 5 15427 7 and 36505 21 (2s nfrac14 5)respectively long-term reproducibility for the same ratiosyielded the following values 16888 8 15424 9 and36495 27 (2s n frac14 102) respectively An averagefractionation factor of 0149 per mass unit relative tothe reference values of Thirlwall (2000) was applied to allPb isotope ratios The accuracy of Pb isotope data wasfurther tested by replicate measurements of AGV-1 yield-ing averages of 206Pb204Pb 18940 0014 (2s n frac14 11)207Pb204Pb 15653 0017 (2s n frac14 11) 208Pb204Pb38566 0061 (2s n frac14 11) which are within error ofthe values reported by Weis et al (2006) Analytical detailsare provided in Avanzinelli et al (2005) All data alongwith standard reproducibility are reported in Tables 4 and5 internal errors have been fully propagated to account forthe added imprecision due to age correction

4 Petrography and classification

The Pachino-Capo Passero outcrops represent a formersmall volcanic island characterised by submarine to sub-aerial volcanic products Submarine lavas are charac-terised by brecciation with jigsaw fit texture filled up byaltered hyaloclastic glass or secondary carbonate material(ESM 1a) The freshest samples show porphyritic to glo-meroporphyritic textures (Porphyritic Index hereafter PIfrac14 8ndash19 ESM 3) Phenocrysts are made of olivine zonedT

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alk

m

ild

lyal

kal

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Mg

-

[Mg

(M

gthorn

08

5

Fe2thorn

)

78 R Avanzinelli GT Sapienza S Conticelli

clinopyroxene and subordinate opaques set in a micro-crystalline groundmass made up of dominant plagioclaseand subordinate olivine clinopyroxene and opaque miner-als The strongly altered samples display serpentine afterolivine with altered clinopyroxene and groundmass andabundant secondary calcite Two dykes intruding the

submarine sequence of lava flows have been found theyhave fairly different petrographic characteristics from por-phyriticglomeroporphyritic (PAC 8 PI frac14 25 ESM 3)to almost aphyric textures (PAC 5 ESM 3) The porphyri-ticglomeroporphyritic dyke shows phenocrysts of freshplagioclase iddingsitised olivine and rare clinopyroxene

Table 3 Major (wt) and trace elements (ppm) for selected samples from La Queglia and Pietre Nere dykes

Sample NPM 15 NPM 17 NPM 13 NPM 2 NPM 3 NPM 5Group PN PN LQ LQ LQ LQ

SiO2 3954 4019 3645 3581 3557 3571TiO2 4946 333 352 351 3889 3835Al2O3 1092 1074 1135 934 1026 1087Fe2O3 591 617 754 726 1167 1132FeO 875 758 389 329 ndash ndashMnO 0180 013 012 016 0187 0181MgO 666 827 1394 1688 1582 1465CaO 1094 1396 1026 1302 918 979Na2O 169 157 074 049 057 069K2O 495 418 140 081 145 131P2O5 137 095 145 113 147 146LOI 387 284 889 816 952 882Sum 9972 9990 9955 9984 9959 9864Mg- 8842 7576 8116 8442 8542 8742Sc 20 ndash 300 365 19 16Be ndash ndash ndash ndash ndash ndashV 352 281 391 389 350 381Cr 90 170 311 388 300 220Co 42 386 460 511 46 43Ni 70 954 177 233 170 140Cu 70 ndash ndash ndash 60 60Zn 140 ndash ndash ndash 110 110Ga 24 ndash ndash ndash 20 20Ge 2 ndash ndash ndash 1 1Rb 92 51 44 28 38 35Sr 814 673 1560 988 1869 2665Y 32 30 18 26 30 30Zr 498 372 475 393 404 403Nb 126 96 142 130 121 123Sb 05 ndash ndash ndash 05 05Cs 12 ndash ndash ndash 05 05Ba 1292 1062 1140 1140 1185 1124La 102 751 730 815 872 811Ce 203 1464 950 1317 148 132Pr 230 ndash ndash 133 156 140Nd 909 687 43 591 601 541Sm 161 129 758 115 116 104Eu 449 387 286 364 333 305Gd 143 ndash ndash 116 111 102Tb 16 146 105 133 13 13Dy 72 ndash ndash 723 62 60Ho 12 ndash ndash 115 10 10Er 28 ndash ndash 295 26 25Tm 034 ndash ndash 037 033 032Yb 19 187 207 210 19 19Lu 027 026 028 029 027 027Hf 104 1171 115 117 81 74Ta 81 745 450 461 58 52Pb 60 48 60 75 75 90Th 108 87 51 91 85 67U 35 285 31 33 36 33

LQ La Queglia PN Pietre Nere Mg- [Mg(Mgthorn085Fe2thorn)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 79

with accessory opaques set in a microcrystalline intersertalgroundmass The aphyric dyke shows rare clinopyroxenephenocrysts set in a micro- to cryptocrystalline trachyticgroundmass made of plagioclase clinopyroxene olivineand opaques

Subaerial lava flows overlying Rudist-bearing carbonatesmade up a small lava plateau in the peripheral sectors of thevolcanic area whereas close to the village of Pachino in thecentral sector of the volcanic area (Fig 1c) blocky lavas andminor reddish scoriae are piled up to form a gentle hill (ieCozzo Santa Lucia hill Fig 1c) which might have been thesite of a possible subaerial erupting centre Two types ofsubaerial lava flows are found in term of petrographic char-acteristics the mildly porphyritic and the melanocratic onesThe former have porphyritic to glomeroporphyritic textureswith phenocrysts of olivine clinopyroxene minor opaquesand rare plagioclase (Samples PAC 13ndash15 Table 1 ESM 3)set in a microcrystalline groundmass consisting of the samephases of the phenocryst population Melanocratic lava flowsshow highly porphyritic textures (PAC 16ndash17 and 19ndash21 PIfrac14 18ndash50 ESM 3) with abundant olivine and clinopyroxenephenocrysts beside minor opaques and plagioclase set in anintergranular groundmass Olivine shows incipient iddingsi-tisation Some melanocratic lava samples (ie PAC 19) havethe highest porphyritic index associated to the coarsest grainsize (ESM 3) In these lavas olivine and clinopyroxene arethe most abundant phenocrysts with subordinate plagioclaseRare glomeroporphiric aggregates made of plagioclase andclinopyroxene also occur Reddish scoriae are highly vesi-culated with aphyric to glassy textures Rare small-sized

plagioclase crystals are the sole phenocrysts which are dis-persed in a glassy to trachytic groundmass Some iddingsi-tised olivine crystals also occur in the groundmass

The La Queglia dyke shows an intersertal holocrystal-line texture with skeletal to elongated olivine crystalsbeside abundant phlogopite and clinopyroxene minoramphibole K-feldspar and opaques and accessoryamounts of perovskite and apatite Variable amount ofcalcite of debatable nature is also found (Vichi et al2004) The Pietre Nere melasyenitic dyke (De Fino et al1981) has an intersertal holocrystalline texture with abun-dant K-feldspar clinopyroxene biotite and amphibole asprimary phases with accessory titanite and apatite andcalcite among the secondary phases

From a chemical point of view the studied samples areclassified according to the total alkali-silica diagram (TASFig 2 Le Bas et al 1986) two groups might be distin-guished within the Pachino ndash Capo Passero samples on thebasis of different enrichment in alkali defining twoslightly distinct differentiation trends The two groups aredefined hereafter as Na-alkaline and a mildly alkaline andwill be used in the following discussion

Volcanic rocks belonging to the alkaline group range incompositions from basanite to hawaiite passing throughtephrite (Fig 2) This group includes the dykes and twoperipheral lava flows (ie PAC 14 and PAC 15) samplePAC 18 also belongs to the alkaline group although itpresents clear evidence of weathering The lavas of themildly alkaline group range in composition from picroba-salt to alkali basalt with the most differentiated sample

Table 4 Sr-Nd isotope data of Pachino ndash Capo Passero Upper Cretaceous volcanic rocks Pietre Nere melasyenite La Queglia lamprophyre

Age Rb Sr Nd Sm 87Sr86Sr 87Sr86Sr 143Nd144Nd 143Nd144NdMa ppm ppm ppm ppm measured 2 se initial 2 se measured 2 se initial 2 se

Pachino-Capo PasseroPAC 05 707 2 270 731 564 111 0703502 0000006 0703395 0000010 ndash ndash ndashPAC 08 707 2 269 689 410 870 0703244 0000006 0703130 0000011 0512921 0000005 0512862 0000006PAC 14 707 2 960 639 386 779 0703172 0000006 0703128 0000007 0512883 0000005 0512827 0000007PAC 15 707 2 150 575 349 733 0703151 0000006 0703075 0000008 ndash ndash ndashPAC 01 707 2 250 579 462 941 0703174 0000006 0703049 0000012 ndash ndash ndashPAC 02 707 2 174 546 317 700 0703357 0000006 0703265 0000010 0512894 0000005 0512833 0000007PAC 03 707 2 160 558 312 676 0703375 0000006 0703291 0000009 ndash ndash ndashPAC 09 707 2 300 595 470 842 0703386 0000006 0703240 0000013 ndash ndash ndashPAC 16 707 2 130 426 264 582 0703299 0000008 0703210 0000010 ndash ndash ndashPAC 17 707 2 140 454 300 644 0703013 0000006 0702924 0000009 ndash ndash ndashPAC 19 707 2 114 323 218 502 0703168 0000006 0703066 0000010 0512902 0000005 0512837 0000007PAC 21 707 2 145 533 265 605 0703504 0000005 0703425 0000008 0512884 0000004 0512821 0000006PAC 04 707 2 1 133 059 015 0707267 0000006 0707245 0000006 ndash ndash ndash

Pietre Nere foiditeNPM 15 622 08 92 814 909 161 0704058 0000006 0703769 0000023 0512830 0000007 0512786 0000008NPM 17 622 08 51 673 687 129 0704070 0000007 0703877 0000016 0512752 0000004 0512706 0000005

Mt La Queglia lamprophyreNPM 13 40 44 1560 430 758 0703440 0000009 0703394 0000010 0512891 0000006 0512863 0000006NPM 2 40 28 988 591 115 0703429 0000006 0703383 0000007 0512930 0000004 0512899 0000005NPM 3 40 38 1869 601 116 0703762 0000007 0703728 0000007 ndash ndash ndashNPM 5 40 35 2665 541 104 0703584 0000005 0703562 0000005 ndash ndash ndash

Ages after Barberi et al (1974) and Bigazzi et al (1996) ages for La Queglia dyke are estimates after Bianchini et al (2008) NPM 13 andNPM 15 data are from Conticelli et al (2007) Standard errors (2 se) on initial isotope ratios are propagated through a Monte-Carlosimulation assuming 5 error on Rb Sr Sm and Nd concentrations

80 R Avanzinelli GT Sapienza S Conticelli

clinopyroxene and subordinate opaques set in a micro-crystalline groundmass made up of dominant plagioclaseand subordinate olivine clinopyroxene and opaque miner-als The strongly altered samples display serpentine afterolivine with altered clinopyroxene and groundmass andabundant secondary calcite Two dykes intruding the

submarine sequence of lava flows have been found theyhave fairly different petrographic characteristics from por-phyriticglomeroporphyritic (PAC 8 PI frac14 25 ESM 3)to almost aphyric textures (PAC 5 ESM 3) The porphyri-ticglomeroporphyritic dyke shows phenocrysts of freshplagioclase iddingsitised olivine and rare clinopyroxene

Table 3 Major (wt) and trace elements (ppm) for selected samples from La Queglia and Pietre Nere dykes

Sample NPM 15 NPM 17 NPM 13 NPM 2 NPM 3 NPM 5Group PN PN LQ LQ LQ LQ

SiO2 3954 4019 3645 3581 3557 3571TiO2 4946 333 352 351 3889 3835Al2O3 1092 1074 1135 934 1026 1087Fe2O3 591 617 754 726 1167 1132FeO 875 758 389 329 ndash ndashMnO 0180 013 012 016 0187 0181MgO 666 827 1394 1688 1582 1465CaO 1094 1396 1026 1302 918 979Na2O 169 157 074 049 057 069K2O 495 418 140 081 145 131P2O5 137 095 145 113 147 146LOI 387 284 889 816 952 882Sum 9972 9990 9955 9984 9959 9864Mg- 8842 7576 8116 8442 8542 8742Sc 20 ndash 300 365 19 16Be ndash ndash ndash ndash ndash ndashV 352 281 391 389 350 381Cr 90 170 311 388 300 220Co 42 386 460 511 46 43Ni 70 954 177 233 170 140Cu 70 ndash ndash ndash 60 60Zn 140 ndash ndash ndash 110 110Ga 24 ndash ndash ndash 20 20Ge 2 ndash ndash ndash 1 1Rb 92 51 44 28 38 35Sr 814 673 1560 988 1869 2665Y 32 30 18 26 30 30Zr 498 372 475 393 404 403Nb 126 96 142 130 121 123Sb 05 ndash ndash ndash 05 05Cs 12 ndash ndash ndash 05 05Ba 1292 1062 1140 1140 1185 1124La 102 751 730 815 872 811Ce 203 1464 950 1317 148 132Pr 230 ndash ndash 133 156 140Nd 909 687 43 591 601 541Sm 161 129 758 115 116 104Eu 449 387 286 364 333 305Gd 143 ndash ndash 116 111 102Tb 16 146 105 133 13 13Dy 72 ndash ndash 723 62 60Ho 12 ndash ndash 115 10 10Er 28 ndash ndash 295 26 25Tm 034 ndash ndash 037 033 032Yb 19 187 207 210 19 19Lu 027 026 028 029 027 027Hf 104 1171 115 117 81 74Ta 81 745 450 461 58 52Pb 60 48 60 75 75 90Th 108 87 51 91 85 67U 35 285 31 33 36 33

LQ La Queglia PN Pietre Nere Mg- [Mg(Mgthorn085Fe2thorn)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 79

with accessory opaques set in a microcrystalline intersertalgroundmass The aphyric dyke shows rare clinopyroxenephenocrysts set in a micro- to cryptocrystalline trachyticgroundmass made of plagioclase clinopyroxene olivineand opaques

Subaerial lava flows overlying Rudist-bearing carbonatesmade up a small lava plateau in the peripheral sectors of thevolcanic area whereas close to the village of Pachino in thecentral sector of the volcanic area (Fig 1c) blocky lavas andminor reddish scoriae are piled up to form a gentle hill (ieCozzo Santa Lucia hill Fig 1c) which might have been thesite of a possible subaerial erupting centre Two types ofsubaerial lava flows are found in term of petrographic char-acteristics the mildly porphyritic and the melanocratic onesThe former have porphyritic to glomeroporphyritic textureswith phenocrysts of olivine clinopyroxene minor opaquesand rare plagioclase (Samples PAC 13ndash15 Table 1 ESM 3)set in a microcrystalline groundmass consisting of the samephases of the phenocryst population Melanocratic lava flowsshow highly porphyritic textures (PAC 16ndash17 and 19ndash21 PIfrac14 18ndash50 ESM 3) with abundant olivine and clinopyroxenephenocrysts beside minor opaques and plagioclase set in anintergranular groundmass Olivine shows incipient iddingsi-tisation Some melanocratic lava samples (ie PAC 19) havethe highest porphyritic index associated to the coarsest grainsize (ESM 3) In these lavas olivine and clinopyroxene arethe most abundant phenocrysts with subordinate plagioclaseRare glomeroporphiric aggregates made of plagioclase andclinopyroxene also occur Reddish scoriae are highly vesi-culated with aphyric to glassy textures Rare small-sized

plagioclase crystals are the sole phenocrysts which are dis-persed in a glassy to trachytic groundmass Some iddingsi-tised olivine crystals also occur in the groundmass

The La Queglia dyke shows an intersertal holocrystal-line texture with skeletal to elongated olivine crystalsbeside abundant phlogopite and clinopyroxene minoramphibole K-feldspar and opaques and accessoryamounts of perovskite and apatite Variable amount ofcalcite of debatable nature is also found (Vichi et al2004) The Pietre Nere melasyenitic dyke (De Fino et al1981) has an intersertal holocrystalline texture with abun-dant K-feldspar clinopyroxene biotite and amphibole asprimary phases with accessory titanite and apatite andcalcite among the secondary phases

From a chemical point of view the studied samples areclassified according to the total alkali-silica diagram (TASFig 2 Le Bas et al 1986) two groups might be distin-guished within the Pachino ndash Capo Passero samples on thebasis of different enrichment in alkali defining twoslightly distinct differentiation trends The two groups aredefined hereafter as Na-alkaline and a mildly alkaline andwill be used in the following discussion

Volcanic rocks belonging to the alkaline group range incompositions from basanite to hawaiite passing throughtephrite (Fig 2) This group includes the dykes and twoperipheral lava flows (ie PAC 14 and PAC 15) samplePAC 18 also belongs to the alkaline group although itpresents clear evidence of weathering The lavas of themildly alkaline group range in composition from picroba-salt to alkali basalt with the most differentiated sample

Table 4 Sr-Nd isotope data of Pachino ndash Capo Passero Upper Cretaceous volcanic rocks Pietre Nere melasyenite La Queglia lamprophyre

Age Rb Sr Nd Sm 87Sr86Sr 87Sr86Sr 143Nd144Nd 143Nd144NdMa ppm ppm ppm ppm measured 2 se initial 2 se measured 2 se initial 2 se

Pachino-Capo PasseroPAC 05 707 2 270 731 564 111 0703502 0000006 0703395 0000010 ndash ndash ndashPAC 08 707 2 269 689 410 870 0703244 0000006 0703130 0000011 0512921 0000005 0512862 0000006PAC 14 707 2 960 639 386 779 0703172 0000006 0703128 0000007 0512883 0000005 0512827 0000007PAC 15 707 2 150 575 349 733 0703151 0000006 0703075 0000008 ndash ndash ndashPAC 01 707 2 250 579 462 941 0703174 0000006 0703049 0000012 ndash ndash ndashPAC 02 707 2 174 546 317 700 0703357 0000006 0703265 0000010 0512894 0000005 0512833 0000007PAC 03 707 2 160 558 312 676 0703375 0000006 0703291 0000009 ndash ndash ndashPAC 09 707 2 300 595 470 842 0703386 0000006 0703240 0000013 ndash ndash ndashPAC 16 707 2 130 426 264 582 0703299 0000008 0703210 0000010 ndash ndash ndashPAC 17 707 2 140 454 300 644 0703013 0000006 0702924 0000009 ndash ndash ndashPAC 19 707 2 114 323 218 502 0703168 0000006 0703066 0000010 0512902 0000005 0512837 0000007PAC 21 707 2 145 533 265 605 0703504 0000005 0703425 0000008 0512884 0000004 0512821 0000006PAC 04 707 2 1 133 059 015 0707267 0000006 0707245 0000006 ndash ndash ndash

Pietre Nere foiditeNPM 15 622 08 92 814 909 161 0704058 0000006 0703769 0000023 0512830 0000007 0512786 0000008NPM 17 622 08 51 673 687 129 0704070 0000007 0703877 0000016 0512752 0000004 0512706 0000005

Mt La Queglia lamprophyreNPM 13 40 44 1560 430 758 0703440 0000009 0703394 0000010 0512891 0000006 0512863 0000006NPM 2 40 28 988 591 115 0703429 0000006 0703383 0000007 0512930 0000004 0512899 0000005NPM 3 40 38 1869 601 116 0703762 0000007 0703728 0000007 ndash ndash ndashNPM 5 40 35 2665 541 104 0703584 0000005 0703562 0000005 ndash ndash ndash

Ages after Barberi et al (1974) and Bigazzi et al (1996) ages for La Queglia dyke are estimates after Bianchini et al (2008) NPM 13 andNPM 15 data are from Conticelli et al (2007) Standard errors (2 se) on initial isotope ratios are propagated through a Monte-Carlosimulation assuming 5 error on Rb Sr Sm and Nd concentrations

80 R Avanzinelli GT Sapienza S Conticelli

with accessory opaques set in a microcrystalline intersertalgroundmass The aphyric dyke shows rare clinopyroxenephenocrysts set in a micro- to cryptocrystalline trachyticgroundmass made of plagioclase clinopyroxene olivineand opaques

Subaerial lava flows overlying Rudist-bearing carbonatesmade up a small lava plateau in the peripheral sectors of thevolcanic area whereas close to the village of Pachino in thecentral sector of the volcanic area (Fig 1c) blocky lavas andminor reddish scoriae are piled up to form a gentle hill (ieCozzo Santa Lucia hill Fig 1c) which might have been thesite of a possible subaerial erupting centre Two types ofsubaerial lava flows are found in term of petrographic char-acteristics the mildly porphyritic and the melanocratic onesThe former have porphyritic to glomeroporphyritic textureswith phenocrysts of olivine clinopyroxene minor opaquesand rare plagioclase (Samples PAC 13ndash15 Table 1 ESM 3)set in a microcrystalline groundmass consisting of the samephases of the phenocryst population Melanocratic lava flowsshow highly porphyritic textures (PAC 16ndash17 and 19ndash21 PIfrac14 18ndash50 ESM 3) with abundant olivine and clinopyroxenephenocrysts beside minor opaques and plagioclase set in anintergranular groundmass Olivine shows incipient iddingsi-tisation Some melanocratic lava samples (ie PAC 19) havethe highest porphyritic index associated to the coarsest grainsize (ESM 3) In these lavas olivine and clinopyroxene arethe most abundant phenocrysts with subordinate plagioclaseRare glomeroporphiric aggregates made of plagioclase andclinopyroxene also occur Reddish scoriae are highly vesi-culated with aphyric to glassy textures Rare small-sized

plagioclase crystals are the sole phenocrysts which are dis-persed in a glassy to trachytic groundmass Some iddingsi-tised olivine crystals also occur in the groundmass

The La Queglia dyke shows an intersertal holocrystal-line texture with skeletal to elongated olivine crystalsbeside abundant phlogopite and clinopyroxene minoramphibole K-feldspar and opaques and accessoryamounts of perovskite and apatite Variable amount ofcalcite of debatable nature is also found (Vichi et al2004) The Pietre Nere melasyenitic dyke (De Fino et al1981) has an intersertal holocrystalline texture with abun-dant K-feldspar clinopyroxene biotite and amphibole asprimary phases with accessory titanite and apatite andcalcite among the secondary phases

From a chemical point of view the studied samples areclassified according to the total alkali-silica diagram (TASFig 2 Le Bas et al 1986) two groups might be distin-guished within the Pachino ndash Capo Passero samples on thebasis of different enrichment in alkali defining twoslightly distinct differentiation trends The two groups aredefined hereafter as Na-alkaline and a mildly alkaline andwill be used in the following discussion

Volcanic rocks belonging to the alkaline group range incompositions from basanite to hawaiite passing throughtephrite (Fig 2) This group includes the dykes and twoperipheral lava flows (ie PAC 14 and PAC 15) samplePAC 18 also belongs to the alkaline group although itpresents clear evidence of weathering The lavas of themildly alkaline group range in composition from picroba-salt to alkali basalt with the most differentiated sample

Table 4 Sr-Nd isotope data of Pachino ndash Capo Passero Upper Cretaceous volcanic rocks Pietre Nere melasyenite La Queglia lamprophyre

Age Rb Sr Nd Sm 87Sr86Sr 87Sr86Sr 143Nd144Nd 143Nd144NdMa ppm ppm ppm ppm measured 2 se initial 2 se measured 2 se initial 2 se

Pachino-Capo PasseroPAC 05 707 2 270 731 564 111 0703502 0000006 0703395 0000010 ndash ndash ndashPAC 08 707 2 269 689 410 870 0703244 0000006 0703130 0000011 0512921 0000005 0512862 0000006PAC 14 707 2 960 639 386 779 0703172 0000006 0703128 0000007 0512883 0000005 0512827 0000007PAC 15 707 2 150 575 349 733 0703151 0000006 0703075 0000008 ndash ndash ndashPAC 01 707 2 250 579 462 941 0703174 0000006 0703049 0000012 ndash ndash ndashPAC 02 707 2 174 546 317 700 0703357 0000006 0703265 0000010 0512894 0000005 0512833 0000007PAC 03 707 2 160 558 312 676 0703375 0000006 0703291 0000009 ndash ndash ndashPAC 09 707 2 300 595 470 842 0703386 0000006 0703240 0000013 ndash ndash ndashPAC 16 707 2 130 426 264 582 0703299 0000008 0703210 0000010 ndash ndash ndashPAC 17 707 2 140 454 300 644 0703013 0000006 0702924 0000009 ndash ndash ndashPAC 19 707 2 114 323 218 502 0703168 0000006 0703066 0000010 0512902 0000005 0512837 0000007PAC 21 707 2 145 533 265 605 0703504 0000005 0703425 0000008 0512884 0000004 0512821 0000006PAC 04 707 2 1 133 059 015 0707267 0000006 0707245 0000006 ndash ndash ndash

Pietre Nere foiditeNPM 15 622 08 92 814 909 161 0704058 0000006 0703769 0000023 0512830 0000007 0512786 0000008NPM 17 622 08 51 673 687 129 0704070 0000007 0703877 0000016 0512752 0000004 0512706 0000005

Mt La Queglia lamprophyreNPM 13 40 44 1560 430 758 0703440 0000009 0703394 0000010 0512891 0000006 0512863 0000006NPM 2 40 28 988 591 115 0703429 0000006 0703383 0000007 0512930 0000004 0512899 0000005NPM 3 40 38 1869 601 116 0703762 0000007 0703728 0000007 ndash ndash ndashNPM 5 40 35 2665 541 104 0703584 0000005 0703562 0000005 ndash ndash ndash

Ages after Barberi et al (1974) and Bigazzi et al (1996) ages for La Queglia dyke are estimates after Bianchini et al (2008) NPM 13 andNPM 15 data are from Conticelli et al (2007) Standard errors (2 se) on initial isotope ratios are propagated through a Monte-Carlosimulation assuming 5 error on Rb Sr Sm and Nd concentrations

80 R Avanzinelli GT Sapienza S Conticelli

Tab

le5

P

bis

oto

pe

dat

ao

fP

ach

ino

ndashC

apo

Pas

sero

Up

per

Cre

tace

ou

sv

olc

anic

rock

sP

ietr

eN

ere

mel

asy

enit

eL

aQ

ueg

lia

lam

pro

ph

yre

Ag

eP

bT

hU

20

6P

b2

04P

b2

se

20

7P

b2

04P

b2

se

20

8P

b2

04P

b2

se

m

20

6P

b2

04P

b2

se

20

7P

b2

04P

b2

se

20

8P

b2

04P

b2

se

Ma

pp

mp

pm

pp

mm

easu

red

mea

sure

dm

easu

red

init

ial

init

ial

init

ial

Pac

hin

o-C

apo

Pas

sero

PA

C0

57

07

23

85

50

18

22

04

15

00

11

15

69

50

01

03

99

96

00

31

31

92

00

63

00

29

15

67

80

01

03

96

46

00

42

PA

C0

87

07

22

35

58

19

82

03

40

00

11

15

68

40

01

03

99

71

00

31

57

31

97

83

00

50

15

66

50

01

03

94

11

00

55

PA

C1

47

07

21

73

35

11

42

04

50

00

11

15

69

60

01

04

00

77

00

31

44

81

99

56

00

40

15

67

30

01

03

96

01

00

49

PA

C1

57

07

22

32

78

09

32

04

35

00

11

15

69

40

01

03

99

44

00

31

26

92

01

38

00

25

15

68

00

01

03

96

53

00

39

PA

C0

17

07

25

84

30

14

22

01

66

00

10

15

67

60

01

03

97

82

00

31

16

21

99

87

00

18

15

66

80

01

03

96

04

00

34

PA

C0

27

07

21

72

64

08

92

02

02

00

10

15

69

70

01

03

99

36

00

31

34

81

98

19

00

30

15

67

90

01

03

95

63

00

42

PA

C0

37

07

24

82

70

07

62

00

95

00

10

15

71

00

01

03

98

47

00

31

10

51

99

79

00

14

15

70

50

01

03

97

12

00

32

PA

C0

97

07

28

68

17

26

41

99

40

00

10

15

67

30

01

03

96

12

00

31

20

21

97

17

00

22

15

66

30

01

03

93

85

00

37

PA

C1

67

07

21

52

11

07

62

04

88

00

11

15

69

20

01

03

99

11

00

31

33

82

01

15

00

31

15

67

50

01

03

95

72

00

39

PA

C1

77

07

21

52

31

06

92

04

49

00

11

15

67

80

01

03

99

45

00

31

30

62

01

11

00

29

15

66

20

01

03

95

74

00

43

PA

C1

97

07

20

91

76

05

82

04

52

00

11

15

70

80

01

04

01

05

00

31

43

01

99

77

00

38

15

68

50

01

03

96

32

00

47

PA

C2

17

07

21

22

26

07

82

04

44

00

11

15

70

10

01

04

00

48

00

31

43

41

99

66

00

38

15

67

80

01

03

95

93

00

46

Pie

tre

Ner

efo

idit

eN

PM

15

62

2

08

60

01

08

35

20

03

80

01

01

57

11

00

10

39

74

30

03

13

86

19

66

40

02

91

56

93

00

10

39

36

40

04

1N

PM

17

62

2

08

47

58

65

28

52

00

40

00

10

15

71

60

01

03

97

50

00

31

39

71

96

55

00

31

15

69

80

01

03

93

67

00

42

Mt

La

Qu

egli

ala

mp

rop

hy

reN

PM

13

40

60

50

53

10

19

94

00

01

01

57

20

00

10

39

49

00

03

13

40

19

72

90

02

21

57

10

00

10

39

37

70

03

3N

PM

24

07

59

10

33

02

06

49

00

11

15

71

50

01

04

07

65

00

32

29

72

04

64

00

20

15

70

60

01

04

05

97

00

35

NP

M3

40

75

85

03

60

20

12

20

01

01

56

72

00

10

39

79

70

03

13

18

19

92

40

02

11

56

63

00

10

39

64

40

03

5N

PM

54

09

06

70

33

02

03

62

00

11

15

69

60

01

04

00

97

00

31

24

52

02

10

00

17

15

68

90

01

03

99

95

00

33

Inte

rnat

ion

alst

and

ard

rep

rod

ucb

ilit

y

20

6P

b2

04P

b2s

20

7P

b2

04P

b2s

20

8P

b2

04P

b2s

mea

sure

dab

sm

easu

red

abs

mea

sure

dab

s5

mea

n1

68

91

00

05

15

42

70

00

73

65

05

00

21

SR

M9

81

-w

ith

inru

nre

pro

du

cib

ilit

y1

st4

mea

n1

68

85

00

05

15

42

20

00

73

64

93

00

21

SR

M9

81

ndashw

ith

inru

nre

pro

du

cib

ilit

y2

nd

10

1m

ean

16

88

70

00

91

54

23

00

10

36

49

30

02

9S

RM

98

1ndash

lon

gte

rmre

pro

du

cib

ilit

y1

1m

ean

18

94

00

01

41

56

53

00

17

38

56

60

06

1A

GV

1st

and

ard

18

94

01

56

53

38

56

0A

GV

1re

fere

nce

val

ue

afte

rW

eis

eta

l(2

00

6)

mfrac14

23

8U

20

4P

b

frac14

nu

mb

ero

fan

aly

ses

absfrac14

abso

lute

D

ata

for

sam

ple

NP

M1

3(L

aQ

ueg

lia)

and

NP

M1

5ar

en

ewm

easu

rem

ents

wit

hre

spec

tto

that

rep

ort

edin

Co

nti

cell

iet

al

(20

07

)A

ges

asin

Tab

le3

S

tan

dar

der

rors

(2s

e)

on

init

ial

iso

top

era

tio

sar

ep

rop

agat

edb

yM

on

te-C

arlo

sim

ula

tio

nas

sum

ing

5

erro

ro

nU

T

han

dP

bco

nce

ntr

atio

ns

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 81

falling within the hawaiite field (Fig 2) This groupincludes all the submarine lava flows (PAC 1ndash3) and themelanocratic lavas sampled both at Cozzo S Lucia (PAC21) and south-west of the village of Pachino (PAC 16 andPAC 17) The sample PAC 9 falls at the high silica end ofthe dataset (Fig 2) in a position that could belong to eithergroup we included it in the mildly alkaline trend on thebasis of field association

The four samples from the lamprophyric dyke of LaQueglia fall within the foiditic field still well above thealkalinesub-alkaline divide of Irvine amp Baragar (1971)whereas the melasyenitic dyke of Pietre Nere point falls atthe edge of the tephritebasanite field of the TAS diagram(Fig 2)

5 Mineral chemistry

Mineral-chemical data from the Pachino ndash Capo Passerorocks are available as electronic supplementary material(ESM 2)

Olivine is forsterite-rich (Fo70ndash85) with limited core-rimzoning forsterite contents are between 79 and 85 in phe-nocrysts cores and between 70 and 77 in rims These valuesare well within the range for other Na-alkaline basalts fromthe Sicily Channel (Avanzinelli et al 2004) CaO contentnever exceeds 036 wt (ESM 2) contrary to K-alkalineItalian rocks where high CaO values are found at compar-able forsterite contents (eg Perini amp Conticelli 2002Boari amp Conticelli 2007 Conticelli et al 2010) Noanalyses of olivine are available for the Pietre Nere lam-prophyre due to the strong replacement by iddingsite

Clinopyroxene from Pachino-Capo Passero volcanicrocks has invariably a diopsidic composition (Fig 3) dis-tinguishing it from clinopyroxene in Quaternary Na-alkaline

rocks of the Sicily Channel and of Paleocene Na-Alkalinerocks from Pietre Nere and La Queglia where clinopyrox-ene ranges from diopsidic to augitic and ferro-augitic com-positions (De Fino et al 1983 Avanzinelli et al2004)(ESM 2) Al2O3 and TiO2 are extremely variable ran-ging from 29 to 94 wt and from 09 to 39 wt respec-tively (ESM 2) and usually increase from core to rim inweakly zoned clinopyroxene with rims overlapping thecompositions of clinopyroxene microliths from the ground-mass Mg is high with values within the range 75ndash88

Feldspar phenocrysts are present in four out of fiveanalysed samples of the Pachino-Capo Passero volcanicrocks They are prevalently poorly zoned plagioclase butalbite-rich and sanidine compositions are also found asmicrolites of the groundmass of some melanocratic sub-aerial lava flows (ESM 2) Figure 4 shows the Ab-An-Orternary classification for feldspars Plagioclase pheno-crysts range in composition from bytownite (PAC 19 frac14Ab19ndash28An71ndash81Or0ndash1) to labradorite (PAC 08 and PAC 12frac14 Ab30ndash43An55ndash69Or0ndash2) Groundmass plagioclase is lab-radorite to andesine in all samples A few anorthoclase(Ab68An19Or13) microlites coexist with andesine-labrador-ite microlites (Ab35ndash52An44ndash63Or2ndash4) in the groundmass ofsample PAC21 (Fig 4)

35 40 45 50 55 60 65 700

2

4

6

8

10

12

14

(Na 2O

+ K

2O)

wt

SiO2 wt

Monte La Queglia foiditic dyke Punta delle Pietre Nere melasyenite

Capo Passero - alkaline lavas

Capo Passero - mildly alkaline lavas

Irvine amp Baaragar (1971)

Fig 2 Total Alkali-Silica (TAS Le Bas et al 1986) diagram for theCretaceous lavas from Pachino-Capo Passero Pietre Nere melasye-nite and Monte La Queglia dyke The dashed curve divides thealkaline and sub-alkaline fields (Irvine amp Baragar 1971) All con-centrations are recalculated on a water-free basis

Wo

En Fs

diopside hedenbergite

augite

PAC21

En

diopside hedenbergite

augite

PAC08

Fs

En

diopside hedenbergiteaugite

PAC19

Fs

En

diopside hedenbergite

augite

PAC12

Fs

En

diopside hedenbergite

augite

PAC15

Fs

Fig 3 Classification of clinopyroxene compositions from Pachino-Capo Passero rocks (Morimoto 1988) Wo frac14 wollastonite En frac14enstatite Fs frac14 ferrosilite Full circle frac14 clinopyroxene core opencircle frac14 clinopyroxene rim asterisk frac14 clinopyroxene in ground-mass Grain cores (full black circles) inner rim (full grey circles)rims (open circles) and groundmasses (asterisks) are reported asdifferent symbols

82 R Avanzinelli GT Sapienza S Conticelli

falling within the hawaiite field (Fig 2) This groupincludes all the submarine lava flows (PAC 1ndash3) and themelanocratic lavas sampled both at Cozzo S Lucia (PAC21) and south-west of the village of Pachino (PAC 16 andPAC 17) The sample PAC 9 falls at the high silica end ofthe dataset (Fig 2) in a position that could belong to eithergroup we included it in the mildly alkaline trend on thebasis of field association

The four samples from the lamprophyric dyke of LaQueglia fall within the foiditic field still well above thealkalinesub-alkaline divide of Irvine amp Baragar (1971)whereas the melasyenitic dyke of Pietre Nere point falls atthe edge of the tephritebasanite field of the TAS diagram(Fig 2)

5 Mineral chemistry

Mineral-chemical data from the Pachino ndash Capo Passerorocks are available as electronic supplementary material(ESM 2)

Olivine is forsterite-rich (Fo70ndash85) with limited core-rimzoning forsterite contents are between 79 and 85 in phe-nocrysts cores and between 70 and 77 in rims These valuesare well within the range for other Na-alkaline basalts fromthe Sicily Channel (Avanzinelli et al 2004) CaO contentnever exceeds 036 wt (ESM 2) contrary to K-alkalineItalian rocks where high CaO values are found at compar-able forsterite contents (eg Perini amp Conticelli 2002Boari amp Conticelli 2007 Conticelli et al 2010) Noanalyses of olivine are available for the Pietre Nere lam-prophyre due to the strong replacement by iddingsite

Clinopyroxene from Pachino-Capo Passero volcanicrocks has invariably a diopsidic composition (Fig 3) dis-tinguishing it from clinopyroxene in Quaternary Na-alkaline

rocks of the Sicily Channel and of Paleocene Na-Alkalinerocks from Pietre Nere and La Queglia where clinopyrox-ene ranges from diopsidic to augitic and ferro-augitic com-positions (De Fino et al 1983 Avanzinelli et al2004)(ESM 2) Al2O3 and TiO2 are extremely variable ran-ging from 29 to 94 wt and from 09 to 39 wt respec-tively (ESM 2) and usually increase from core to rim inweakly zoned clinopyroxene with rims overlapping thecompositions of clinopyroxene microliths from the ground-mass Mg is high with values within the range 75ndash88

Feldspar phenocrysts are present in four out of fiveanalysed samples of the Pachino-Capo Passero volcanicrocks They are prevalently poorly zoned plagioclase butalbite-rich and sanidine compositions are also found asmicrolites of the groundmass of some melanocratic sub-aerial lava flows (ESM 2) Figure 4 shows the Ab-An-Orternary classification for feldspars Plagioclase pheno-crysts range in composition from bytownite (PAC 19 frac14Ab19ndash28An71ndash81Or0ndash1) to labradorite (PAC 08 and PAC 12frac14 Ab30ndash43An55ndash69Or0ndash2) Groundmass plagioclase is lab-radorite to andesine in all samples A few anorthoclase(Ab68An19Or13) microlites coexist with andesine-labrador-ite microlites (Ab35ndash52An44ndash63Or2ndash4) in the groundmass ofsample PAC21 (Fig 4)

35 40 45 50 55 60 65 700

2

4

6

8

10

12

14

(Na 2O

+ K

2O)

wt

SiO2 wt

Monte La Queglia foiditic dyke Punta delle Pietre Nere melasyenite

Capo Passero - alkaline lavas

Capo Passero - mildly alkaline lavas

Irvine amp Baaragar (1971)

Fig 2 Total Alkali-Silica (TAS Le Bas et al 1986) diagram for theCretaceous lavas from Pachino-Capo Passero Pietre Nere melasye-nite and Monte La Queglia dyke The dashed curve divides thealkaline and sub-alkaline fields (Irvine amp Baragar 1971) All con-centrations are recalculated on a water-free basis

Wo

En Fs

diopside hedenbergite

augite

PAC21

En

diopside hedenbergite

augite

PAC08

Fs

En

diopside hedenbergiteaugite

PAC19

Fs

En

diopside hedenbergite

augite

PAC12

Fs

En

diopside hedenbergite

augite

PAC15

Fs

Fig 3 Classification of clinopyroxene compositions from Pachino-Capo Passero rocks (Morimoto 1988) Wo frac14 wollastonite En frac14enstatite Fs frac14 ferrosilite Full circle frac14 clinopyroxene core opencircle frac14 clinopyroxene rim asterisk frac14 clinopyroxene in ground-mass Grain cores (full black circles) inner rim (full grey circles)rims (open circles) and groundmasses (asterisks) are reported asdifferent symbols

82 R Avanzinelli GT Sapienza S Conticelli

Oxides of two types are found as micro-phenocrystsdispersed in the groundmass and enclosed in the olivinecores of the Pachino-Capo Passero volcanic rocks Ti-magnetite is generally the main opaque mineral whereaseuhedral chromite is hosted by liquidus olivine (ESM 2)La Queglia lamprophyre shows the occurrence of ilmeniteand Ti-magnetite

6 Bulk-rock geochemistry

61 Major-element compositions

SiO2 and MgO contents vary from 43 to 48 wt and from 32to 18 wt respectively Mg-number is in the range 39ndash71MgO has been chosen as differentiation index although itmight be affected by the occurrence of olivine accumulation(see Section 72) as evidenced by the picrobasalt PAC 19falling below the alkalinesub-alkaline divide (Fig 2) Thevolcanic rocks of the alkaline group (sub-aerial plateau-likelava flow and submarine dykes) show significantly lowersilica and slightly higher TiO2 than the rocks of the mildlyalkaline group (Fig 5) TiO2 in the rocks of the alkalinegroup ranges from 315 to 352 wt whereas the rocks ofthe mildly alkaline group commonly have values 3 wtexcept in the most differentiated lavas (Fig 5) The crystal-rich melanocratic lava (PAC 19) shows the lowest TiO2 (2wt) Al2O3 (93 wt) CaO (96 wt) and alkalis (22wt) but the highest MgO (175 wt) and Fe2O3 (132wt) abundances (Tables 2 and 3 Fig 5)

62 Trace-element distribution

The most primitive rocks of the two groups have relativelyhigh Cr and Ni contents (Tables 2 and 3) The crystal-richmelanocratic sub-aerial lava (PAC 19) shows the highest

Or

An

Ab

PAC21

PAC08

PAC19PAC15

PAC12

sanidineanorthoclase

olig

ocla

sean

desi

nela

brad

orite

byto

wni

te

Grain core

Grain rim

Grain inner rim

Groundmass grain

Fig 4 Classification for feldspars in the studied lavas Ab frac14 albiteAn frac14 anorthite Or frac14 orthoclase Symbols as in Fig 3

MgO wt0 5 10 15 20

30

35

40

45

50

558

10

12

14

16

18

TiO

2 w

t

Na 2

O w

t

Al 2

O3

wt

S

iO2

wt

1

2

3

4

5

0

1

2

3

4

5

6

Tholeiites and tholeiitic basaltsPlio-Pleistocene Hyblean lavas

+X

+X Alkali basalts and basanites

Fig 5 Major oxides (wt) vs MgO (wt) of Cretaceous Pachino-Capo Passero Pietre Nere and La Queglia rocks Literature data forsubalkaline (ie tholeiites lsquolsquothornrsquorsquo) and alkaline (ie alkali basalts andbasanites lsquolsquoxrsquorsquo) rocks of the Neogene magmatism of the Hybleanplateau are reported (data from the GEOROC database httpgeor-ocmpch-mainzgwdgdegeoroc) Other symbols as in Fig 2

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 83

Cr (560 ppm) and Ni (330 ppm) contents whereas it hasvery low concentration of incompatible trace elements(Fig 6) Only small differences between the two groupsare observed in trace element contents (Fig 6) in particu-lar in the most MgO-rich terms the rocks of the alkalinegroup show slightly higher incompatible trace elementcontents than the mildly alkaline ones (Fig 6) Ni and Crare positively correlated with MgO

Chondrite (Ch)-normalized Rare Earth Element (REE)patterns (Fig 7) of the Pachino-Capo Passero volcanicrocks from both alkaline and mildly alkaline groups arecharacterised by the enrichment of Light REE (LREE)over heavy REE (HREE) (LaNYbN frac14 85ndash153)Primordial Mantle normalised incompatible trace elementshave patterns resembling those typical of within-platebasalts The alkaline group shows on average slightlyhigher incompatible trace element abundances than themildly alkaline group (Fig 7) Pietre Nere and LaQueglia dykes have similar fractionated patterns but athigher absolute values (Fig 7) The Rudists-bearing lime-stone is characterized by very low trace-element contents(generally below detection limits) and a flat Chondrite-normalised REE pattern (Fig 7) except for enrichedLaN the Primordial Mantle (PM)-normalised patternsalso reflect the low trace-element contents with normal-ized values 1 except U and Sr (Fig 7)

63 Sr-Nd-Pb isotopes

Initial (ie age corrected) Sr-Nd-Pb isotope data of thePachino Capo Passero rocks are plotted in Fig 6 and 8along with Pietre Nere and La Queglia samples and withliterature data for Hyblean plateau lavas (Trua et al 1998Bianchini et al 1999) The isotopic compositions of vol-canic rocks from the Canary Islands are also plotted forcomparison (Fig 8 see Section 74) No significant differ-ences between the isotopic composition of the alkaline andthe mildly alkaline group are observed 87Sr86Sri and143Nd144Ndi for the Pachino ndash Capo Passero volcanicrocks vary in rather narrow ranges 0703049ndash0703425and 0512821ndash0512862 respectively (Table 4) Samplesfrom La Queglia have higher 143Nd144Nd whilst thosefrom Pietre Nere display significantly higher 87Sr86Sri

Initial 206Pb204Pbi207Pb204Pbi and 208Pb204Pbi values

also vary within the range of 1971ndash2014 1566ndash1570 and3941ndash3971 (Table 5) respectively Pietre Nere dyke hasslightly higher 207Pb204Pbi than Pachino-Capo-Passero vol-canic rocks (Fig 8) at comparable 206Pb204Pbi The foursamples from La Queglia dyke do not show homogenousisotope composition (206Pb204Pbi frac14 1973ndash2046207Pb204Pb frac14 1566ndash1571 208Pb204Pb frac14 3938ndash4060)with values slightly less radiogenic than those reported byBeccaluva et al (2007) These absolute values howevermight be affected by a significant uncertainty due to the poorage constraints on this lamprophyric dyke All but onesamples plot just above the Northern HemisphereReference Line (ie NHRL Hart 1984) in 206Pb204Pb vs207Pb204Pb space with D74 values (ie the difference in

Fig 6 Selected trace-elements (ppm) vs MgO (wt) of CretaceousPachino-Capo Passero Pietre Nere and La Queglia rocks along withliterature data for Neogene Hyblean volcanic rocks (data source andsymbols as in Fig 5) In the last figure are also plotted the composi-tion of crust-derived xenoliths found within Neogene Hyblean lavas(Scribano et al 2006) Symbols as in Fig 5

84 R Avanzinelli GT Sapienza S Conticelli

207Pb204Pb between the sample and the NHRL at the sam-plersquos 206Pb204Pb) between ndash09 and thorn48 On the contraryD84 values (ie the difference in 208Pb204Pb between thesample and the NHRL at the samplersquos 206Pb204Pb) is alwaysnegative between ndash25 and ndash374 Pietre Nere dyke sampleshave significantly higher D74 (7) and D84 (ndash3) thanPachino-Capo Passero rocks whilst La Queglia samplesdisplay variable delta values As a whole all the studiedrocks fall just outside the field of the Common MantleReservoir as defined by Lustrino amp Wilson (2007) (Fig8) They also display slightly more radiogenic Pb isotopecomposition than both the Plio-Pleistocene volcanic pro-ducts of the Hyblean plateau and the Canary Islandswhich instead plot well within the CMR field No evidentcorrelations are observed between isotope ratios and trace-element contents or ratios

7 Discussion

The geochemical characteristic of these magma and thevariations observed within the sample set may depend ondistinct factors such as shallow-level magma differentia-tion en route to the surface (crustal contamination andcrystallisation) different degrees of partial melting ordifferent mantle sources These issues will be discussedin this section along with the possible implications at theregional scale Due to the geographic proximity the UpperCretaceous lavas of Pachino Capo-Passero and theNeogene volcanic products of the neighbouring HybleanPlateau have been normally considered as a single mag-matic suite (eg Carter amp Civetta 1977 Rocchi et al

1998 Lustrino amp Wilson 2007) Plate motions and palaeo-geographic reconstruction indicate however that the posi-tion of SE Sicily and the Pelagian Block during the UpperCretaceous should have been 2000 km SE of its presentposition and more than 1000 km away from the position ofthe same area during the emplacement of the NeogeneHyblean plateau (eg OrsquoConnor et al 1999 Stampfliamp Borel 2002 Piromallo et al 2008 see also thewebsite httpcpgeosystemscomeuropaleogeogra-phyhtml and reference therein) Therefore the assumptionof a unique mantle source for these two magmatic events isclearly an untenable assumption In this context the volcan-ism occurring at Pietre Nere and La Queglia provides aninteresting comparison The Adria Plate seems to havemoved together with the Pelagian block during the conver-gence of Africa and Eurasia (httpcpgeosystemscomeuro-paleogeographyhtml and reference therein) Therefore themantle source of the Pietre Nere melasyenite and the LaQueglia lamprophyre at the time of their eruption (Paleoceneand Eocene respectively) should have been somewhere inbetween the Cretaceous position of the Pachino-CapoPassero and the Neogene location of the Hyblean Plateau

71 Crustal contamination

Being erupted over continental crust the Cretaceous lavasof Pachino-Capo Passero might be prone to contaminationdue to assimilation of continental crust en route to the sur-face As a general rule assimilation of crustal materialshould produce an increase of Sr isotope ratio with decreas-ing MgO content that is not observed in the Pachino-Capo

01

1

10

100

LaCe

PrNd

-Sm

EuGd

TbDy

HoEr

TmYb

Lu

Roc

kC

hond

rite

LaCe

PrNd

-Sm

EuGd

TbDy

HoEr

TmYb

Lu

La Queglia lamprophyric dyke Pietre Nere mela-syenitic dyke Pachino - Capo Passero alkaline Pachino - Capo Passero mildly alkaline

Rudist bearing limestone

CsRb

BaTh

UKTa

NbLa

CeNd

SrPSm

HfZr

EuTi

TbYYb

Lu

001

01

1

10

100

Roc

kP

rimor

dial

Man

tle

CsRb

BaTh

UKTa

NbLa

CeNd

SrPSm

HfZr

EuTi

TbYYb

Lu

Fig 7 Chondrite-normalised REE distribution and Primordial Mantle-normalised incompatible elements distribution for CretaceousPachino-Capo Passero Pietre Nere and La Queglia rocks Chondrite (Ch) and Primordial Mantle (PM) values used for the normalisationare from McDonough amp Sun (1995) and Sun amp McDonough (1989) respectively

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 85

Passero rocks (Fig 6) Halliday et al (1995) showed thatmantle-derived OIB magmas have rather constant values ofkey trace-element ratios such as BaCe (45 13) BaNb(79 23) NbU (48 11) and CePb (35 11) The sameratios are significantly different in the continental crust inthe range 10ndash13 51ndash57 4ndash25 and 35ndash50 respectively(Rudnick amp Gao 2003) The dataset of Pachino-CapoPassero samples presented in this study yields BaCe frac1436 06 (2s n frac14 13) and BaNb frac14 67 12 (2s n frac1413) both within the OIB values of Halliday et al (1995) andwell distinct from crustal values NbU (35 12 2s n frac1413) and CePb (299 22) are still within the range of OIBbut they are more variable due to the anomalously lowvalues of the some low-MgO samples of the mildly alkalinegroup These data might indicate a possible effect of crustalcontamination in the most differentiated rocks

To investigate further this issue we took into considerationthe composition of crustal xenoliths erupted by the NeogeneHyblean magmatism (Tonarini et al 1996 Sapienza ampScribano 2000 Scribano et al 2006) that should be repre-sentative of the continental crust beneath the Pelagian BlockScribano et al (2006) report major trace elements and Srisotope ratios of crustal xenoliths divided into diorites (opendiamonds Fig 9) igneous- and metamorphic-textured (lightand dark grey diamonds Fig 6ndash9) The composition of suchxenoliths is variable with 87Sr86Sr in the range070394ndash070519 (Fig 6) In general they are rather depletedin incompatible trace element with respect to Pachino-CapoPassero lavas with the notable exception of Sr and Ba con-tents reaching values as high as2700 ppm and 2500 ppmrespectively The Sr enrichment of the xenoliths is reflectedin their extremely high SrNb up to two orders of magnitudehigher than ratios measured in the Pachino-Capo Passerolavas (Fig 9) Hence any influence of crustal contaminationin Pachino Capo-Passero should be reflected in an increaseof SrNb along with decreasing MgO content as evidencedby the simple mixing curve in Fig 9a The figure shows thatSrNb is almost constant in the studied samples with the mostdifferentiated samples actually showing slightly lowervalues than the more primitive ones In addition no correla-tion exists between SrNb (or any other indices of crustcontamination) and Sr or Pb isotope ratios (not shown) Wetherefore conclude that crustal contamination does not play asignificant role in the determining the composition of thestudied magmas

72 Shallow-level magma differentiation

Liquid lines of descent for the Pachino-Capo Passero rocksindicate fractionation of olivine clinopyroxene a limitedlate entrance of plagioclase into the fractionating assem-blage might explain the slight flattening of the trend ofAl2O3 towards the most differentiated terms of the alkalinegroup (Fig 5) the same does not occur in the mildly alka-line rocks suggesting that the small amount of plagioclasecrystallised in the late stage of magma differentiation is notefficiently separated Plagioclase is indeed present in veryminor amounts mainly concentrated in the groundmass

143N

d14

4 Nd

i

87Sr86Sri

Canary Islands

C by Cadoux 2007et al

CMR by Lustrino amp Wilson 2007

A)

B)

207 P

b20

4 Pb

i

206Pb 204Pbi

Geo

chro

n

NHRL

25 Ga OC

175 180 185 190 195 200 205 210 2151545

1550

1555

1560

1565

1570

1575

1580

++++ + +

+

++

+

+

+

xx xx

xxx

x

x

x xx

x

x

x

xx x

x

x

25

20

30

μ = 15

11

12

13

μ = 10

15 Ga OC

2σ

07025 07030 07035 07040 07045 0705005122

05124

05126

05128

05130

05132

05134

+ ++

++

+++

++

+

++

xxxxx

x

x

x

xx

x xxx x

x x

xx

xxx

x xxxx

FuerteventuraBasal Complex (gt20 Ma)

Fig 8 Isotopic composition of Cretaceous Pachino-Capo PasseroPietre Nere and La Queglia rocks Data for sample NPM 13 (LaQueglia) and NPM 15 are from Conticelli et al (2002 2007) Data forthe Neogene Hyblean plateau lavas are from Tonarini et al (1996) Truaet al (1998) and Bianchini et al (1999) In order to compare the studiedsamples with that of the Central Mediterranean are also displayed thefield of the Common Mantle Reservoir (CMR) proposed by Lustrino ampWilson (2007) and the lsquolsquoCrsquorsquo component used by Cadoux et al (2007) forsouthern Italy following that suggested by Hanan amp Graham (1996)Isotope composition of volcanic rocks from the Canary Islands (greysquares data from the GEOROC database httpgeorocmpch-main-zgwdgdegeoroc) are also reported as potentially representative of thecommon lsquolsquoplume-relatedrsquorsquo component suggested by Piromallo et al(2008) Samples from the Basal Complex of Fuerteventura (Hoernle ampTilton 1991 de Ignacio et al 2006) are highlighted (dotted squares) asrepresentative of the oldest products of the Canary hot spot Othersymbols as in Fig 2 5 and 6 (a) 143Nd144Nd vs 87Sr86Sr fully agepropagated internal errors are smaller than symbolrsquos size (b)207Pb204Pb vs 206Pb204Pb The North Hemisphere Reference Line(NHRL) is calculated from the equation of Hart (1984) The figurealso shows the composition of two possible oceanic crusts of 25 Ga(long-dashed line) and 15 Ga (short-dashed line) respectively calcu-lated as described in the text The starting composition of depletedMORB mantle is that of the D-DMM reported in Workman amp Hart(2005) Pb frac14 0018 ppm UPb frac14 0131 206Pb204Pb frac14 17573206Pb204Pbfrac14 15404 The black ellipse represents the external reprodu-cibility (2s) of the AGV1 international rock standard The larger greyellipse represents the reproducibility of AGV 1 when an age correction isapplied in order to illustrate the effect of a full error propagation on thereproducibility of the samples the error propagation was performedthrough a Monte-Carlo simulation assuming values for U Th and Pb andage similar to that of Pachino ndash Capo Passero samples (see Table 5)

86 R Avanzinelli GT Sapienza S Conticelli

with the exception the evolved samples of the alkalinegroup (PAC 8 PAC 18 see ESM 3) The weak zonationof plagioclase and clinopyroxene phenocrysts indicatesthat magma storage was not prolonged not even in caseof the crystal-rich picrites PAC 12 and PAC 19 These twosamples have petrographic (PI 50) and geochemicalcharacteristics (available only for sample PAC19 high Crand Ni contents low incompatible elements contents) indi-cating a crystal accumulation rather than a melt-like com-position A smaller amount of accumulated crystals can be

also envisaged for other samples on the basis of geochemicaldata Albarede (1992) suggested that magmas with FeOMgO 09 are likely to be affected by accumulation ofolivine and clinopyroxene Assuming that magmas in equili-brium with their mantle source have 85 of iron in itsreduced form (Frey et al 1978) this converts the limit toFeOtotMgO 106 In Fig 9b the variation of FeOtotMgOvs MgO of Pachino-Capo Passero rocks is plotted togetherwith curves of both cumulus (solid line) and fractionation(dashed line) of a mineral assemblage made up by 60 olivine thorn 35 clinopyroxene thorn5 plagioclase (mineralproportion are estimated from the cumulatic sample PAC 19details are provided in the figure caption) The modelledcurves closely correspond to the composition of the studiedsamples suggesting that as well as PAC 19 the other high-MgO samples of the mildly alkaline group (PAC 16 PAC 17)are likely to include small amount of accumulated crystals

The evidence of both crystal fractionation and accumula-tion imply the presence of a magma chamber where eithermagma can store and differentiate although for limitedtimes andor crystals can accumulate The occurrence of amagma chamber is an important difference with the pro-ducts of Cenozoic magmatic rocks of this area which aremostly undifferentiated and often bear mantle xenoliths asproofs of their rapid ascent from the source to the surface(eg Sapienza amp Scribano 2000 Bianchini et al 2008)

73 Characterization of the source for Pachino CapoPassero Upper Cretaceous lavas

Geochemical (Fig 9) and petrographic characteristics helpto identify which samples of the two groups can be con-sidered to have near-primary compositions These sam-ples namely PAC 14 and PAC 15 of the alkaline groupand PAC2 PAC3 and PAC 21 of the mildly alkaline groupwill be used in this section to investigate the condition ofmantle melting producing the Pachino-Capo Passero mag-mas in comparison with the condition estimated for theNeogene magmatism of the Hyblean Plateau (Beccaluvaet al 1998) It is more difficult to evaluate whether sam-ples from Pietre Nere and La Queglia can be consideredrepresentative of primary magma compositions PietreNere samples have relatively low MgO contents and highFeOtotMgO (Fig 9) indicating they have been affectedby loss of mafic phases On the contrary all samples fromthe La Queglia dyke display extremely high MgO contentsand low FeOtotMgO (down to 058) this suggests exten-sive accumulation of olivine and clinopyroxene althoughpetrographic evidence for it was not found

Near-primary samples can be used to estimating thepressure and temperature conditions of magma genesisaccording to the algorithms of Klein amp Langmuir (1987)and Albarede (1992) These calculations yield values of Tfrac14 1299ndash1370 C and P 15ndash22 kbar for the samples of themildly alkaline group (PAC2 3 and 21) and T frac141377ndash1391 C and P frac14 29 kbar for those of the alkalineone (PAC 14 and 15) The same calculation did not yieldmeaningful data for the samples of the La Queglia dyke

Xenolith avg

Fig 9 A) MgO (wt) vs SrNb of Pachino-Capo Passero PietreNere and La Queglia volcanic rocks along with literature data forNeogene Hyblean Plateau (data source as in Fig 5) The compositionof crust-derived xenoliths is also reported (Sapienza amp Scribano2000 Scribano et al 2006) A mixing line between the averagecomposition of Pachino-Capo Passero near primary magmas (iePAC 2 3 and 21) and the average of the crustal xenoliths fromScribano et al (2006) is reported to show possible effect of crustalcontamination on the studied samples B) MgO (wt) vs FeOtotMgO the two curves model separation (dashed lin) and accumula-tion (solid lines) respectively of a mineral assemblage made up by60 olivinethorn 35 clinopyroxenethorn 5 plagioclase as estimatedfrom petrographic evidences from the cumulitic sample PAC 19Small solid circles onto the curves marks 10 increase of fractio-natedcumulated minerals The curves are modelled through massbalance starting from the same near-primary composition used inFig 9a The major-element composition of the separatedcumulatedmineral phases are assumed as the average (for each phase) of thedata from the clearly cumulitic sample PAC19 (data available inElectronic supplementary material 2) Symbols as in Fig 5

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 87

probably due to the same process responsible for the anom-alously low FeOtotMgO the least evolved Pietre Nerealthough probably not representative of a near-primarycomposition (NPM 17) yielded T frac14 1377 C and P frac14 33kbar Beccaluva et al (1998) performed the same calcula-tion on the Neogene Hyblean volcanic rocks obtaining thefollowing ranges subalkaline basalts (MgO 7 ) 6ndash15kbar 1219ndash1250 C alkali basalts 14ndash19 kbar 1280ndash1320C basanites 16ndash28 kbar 1290ndash1410 C nephelinites24ndash34 kbar 1300ndash1370 C From these data the authorsinferred that the mantle solidi of the Hyblean magmas werevolatile-bearing and so close to the regional geotherm thatpartial melting could be attained by limited decompressionmelting (Fig 10 of Beccaluva et al 1998) Our calcula-tions highlight some differences between the alkaline andmildly alkaline group with the former originating from adeeper and hotter mantle source at pressure and tempera-ture values similar to the highest estimated for NeogeneHyblean basanites shallower melting comparable to thehigher end of the range calculated for the NeogeneHyblean alkali basalts (Beccaluva et al 1998) is sug-gested for the mildly alkaline group In general our

calculations produce for any given estimated pressuretemperatures 20ndash50 C higher than those calculated forNeogene Hyblean magmas This difference is almostwithin the estimatersquos error (40 C) but the consistencyof the shift away from the regional geotherm might indi-cate a slightly more prominent role for decompressionmelting The P conditions of magma segregation estimatedfor the alkaline and mildly alkaline groups correspond to adepth of 95 km and 50ndash70 km respectively consider-ing also the T estimates both groups should have generatedwithin the spinel-peridotite field with the alkaline magmasclose to the transition between the spinel- and the garnet-peridotite stability fields The presence of residual garnet isalso suggested by TbNYbN in the range 249ndash293 and249ndash260 for alkaline and mildly alkaline rocks respec-tively These values are indeed slightly higher than thosereported for alkaline basalts of Hawaii (TbNYbN frac14189ndash245 Frey et al 1991) which are commonlybelieved to have been generated in a garnet-bearing lher-zolitic mantle (Frey et al 1991 McKenzie amp OrsquoNions1991) Samples from the La Queglia lamprophyre displayvariable TbNYbN (226ndash305) but broadly similar to ofPachino-Capo Passero Pietre Nere melasyenite has signif-icantly more fractionated HREE (TbNYbN frac14 349ndash376)consistently with the higher pressures calculated above

Pachino-Capo Passero samples show a typical OIB-typePM-normalized incompatible trace element diagrams(Fig 7) The alkaline and the mildly alkaline samples havesimilar patterns suggesting a genetic linkage between thetwo series Thus both groups derive from a similar mantlesource as also confirmed by Sr Nd and Pb isotopes whichdo not show significant difference between the two groups(Fig 6 and 8) The near primary Cretaceous magmas ofPachino-Capo Passero have trace elements concentrationscomparable with the least enriched alkali basalts of theNeogene Hyblean volcanism and just above the Hybleansub-alkaline products (Fig 6) Samples from Pietre Nereand La Queglia have significantly higher incompatibletrace element contents comparable with the most enrichedalkaline magmas of the Neogene Hyblean plateau (basa-nites and nephelinites) up to four times higher than inPachino-Capo-Passero (Fig 6) To a first approximationtwo main processes might contribute to produce the geo-chemical and isotopic differences both within magmasfrom the same locality and between the different magmaticsuites (i) different degrees of mantle melting of a similarmantle source decreasing from Pachino-Capo Passeromildly alkaline rocks through the alkaline one to PietreNere and La Queglia (ii) different trace-element enrich-ment of the mantle source increasing in the same order

Isotope data in Pachino-Capo Passero rocks are rela-tively homogeneous and do not covariate with any trace-element content or ratio hence suggesting a commonsource for these magmas (Fig 8) On the contrary therocks from Pachino-Capo Passero are isotopically distin-guished from those of Pietre Nere and La Queglia TheNeogene rocks from the Hyblean Plateau also have distinctSr-Nd-Pb isotope composition with respect to the

Tb N

YbN

BaN

0 50 100 150 2000

1

2

3

4

x

x xx xxx xxxx x xx x xxxxxxx

xxx

++ +++

++++

Ti N

0

5

10

15

20

x

xx

xx

x

x

x x

xx

x

xxx

xxx

x

x x

x

x

x

x

x

xx

x

xx

x

x

x xx

xx

xx

xx

xx

xxx

xx

x

xx

x

xx x

x

x

x

++ +

++ +++++

+

+

++

+

++

+

++ +

+

+

+

+ + ++

+

+

A)

B)

Fig 10 BaN vs TiN and TbYbN of Pachino-Capo Passero Pietre Nereand La Queglia volcanic rocks along with literature data for NeogeneHyblean Plateau (data from the GEOROC database httpgeor-ocmpch-mainzgwdgdegeoroc) Chondrite values used for the nor-malisation are from McDonough amp Sun (1995) Symbols as in Fig 5

88 R Avanzinelli GT Sapienza S Conticelli

Cretaceous products of Pachino-Capo Passero hence sug-gesting a different mantle source (Fig 8)

Therefore although estimates of degree of melting canbe attempted for the various magmatic associations (seefollowing discussion) a comparison between Pachino-Capo Passero Pietre Nere and La Queglia might have littlesignificance given the different nature and compositioninferred for their mantle sources A relative estimate ofdegree of melting can be done through Nd isotopes A factoraSmNd can be obtained dividing the measured 147Sm144Ndof the erupted lavas by that estimated for their mantlesources modelled through Nd isotopes the source147Sm144Nd is calculated assuming an evolution of thesample source with chondritic values until at 17 Ga a Sm-Nd fractionation occurs such that the measured143Nd144Nd is produced by the subsequent evolution ofthe mantle to the present day (DePaolo 1988) The near-primary sample from the alkaline group (PAC 14) have aSm

Nd frac14 057 lower than that measured for those of the mildlyalkaline group (PAC 2 frac14 062 PAC 21 frac14 065) indicatingthat the former has been generated by lower degree ofmelting The samples from the roughly coeval activity atPietre Nere and La Queglia have significantly lower aSmNd

(on average 053 and 050 respectively) in this case how-ever some of the fractionation might be ascribed to enrich-ment of the mantle source rather than simply variation in thedegree of melting (see above discussion)

Providing an absolute estimate of the melting degree ismore complicate since the models are heavily depended onthe parameters used for the calculation (mostly the bulkdistribution coefficients D) A first-order estimate can bedone on the basis of highly incompatible trace element con-tents (eg Rb Ba Th Nb La) for which D can be approxi-mated to zero For these elements the enrichment producedby mantle melting is inversely proportional to the degree ofpartial melting (CLC01F Shaw 1970) absolute estimatesof F can thus be calculated once a source composition isassumed Some authors consider the Upper Cretaceouslavas of Pachino Capo-Passero and the Neogene volcanicproducts of the neighbouring Hyblean Plateau to be part ofa single magmatic suite (eg Carter amp Civetta 1977 Rocchiet al 1998 Lustrino amp Wilson 2007) hence being origi-nated from similar mantle sources In this hypothesis we canestimate the degree of partial melting required to generate thestudied rocks starting from the mantle source proposed byBeccaluva et al (1998) (S2 for alkali basalts S1 for tho-leiites) Assuming S2 as mantle source Th and Ba contents ofPachino-Capo Passero rocks require degrees of partial melt-ing between 22 and 33 for Th and between 17 and 25 forBa (the lowest values for the alkaline group) Even using themore depleted S1 source (calculated by Beccaluva et al(1998) for subalkaline products) the enrichment factor yieldsestimates of F too high (17ndash23 for Th and 12ndash17 for Ba)to generate alkaline magmas In particular the high TbYbN ofPachino-Capo Passero lavas could not be generated by suchhigh degree of melting due to the exhaustion of any residualphase able to fractionate HREE

The mantle sources proposed by Beccaluva et al (1998)were interpreted as enriched portion of the lithospheric

subcontinental mantle beneath Sicily Pachino CapoPassero lavas appear to have been generated from a signifi-cantly more depleted likely asthenospheric mantle sourceTherefore the mantle source of Cretaceous and Neogenemagmatism in SE Sicily must be generated by distinctmantle sources as also indicated by palaeogeographic con-sideration and isotope compositions (Fig 8 and 11)

A different more elaborated estimate of the degree ofmelting and source composition can be done through thedynamic-inversion method of Zou amp Zindler (1996) refinedby Zou (1998) and Zou et al (2000) In this approach thedegrees of partial melting and the source composition can becalculated from the ratios between differently incompatibletrace elements in magmas derived from different degree ofmelting Assuming that the difference between alkaline andmildly alkaline samples is only due to different degrees ofpartial melting the different trace-element content betweenthe most enriched (PAC 14) and most depleted (PAC 21)near-primary samples can be used for the calculation (Table6) Although this method is strongly dependent on thechoice of bulk distribution coefficients the results can becompared with those calculated using similar method andparameters for other alkali basalts from Hawaii SEAustralia and SE China (Zou amp Zindler 1996 Zou et al2000) The degrees of partial melting calculated forPachino-Capo Passero using different pairs of highly tomildly incompatible elements are less homogeneous thanthose reported by Zou amp Zindler (1996) and Zou et al(2000) This might be due to inappropriate choice of dis-tribution coefficients or might indicate that the observedgeochemical variability is not uniquely due to differentdegree of partial melting For example slightly differentmantle sources for the alkaline and mildly alkaline rocks

87S

r86

Sr i

208Pb

206Pbi

FOZO

185 190 195 200 205 21007025

07030

07035

07040

07045

07050

++

+

+++++

++

++

x

xxxx

x

xxx xx x

xx

xx

x

x x

HIMU

2σ

Fig 11 87Sr86Sr vs 208Pb206Pb plot for Pachino-Capo PasseroPietre Nere and La Queglia volcanic rocks along with literaturedata for Neogene Hyblean Plateau (Trua et al 1998 Bianchiniet al 1999) and Canary Islands (data from the GEOROC databasehttpgeorocmpch-mainzgwdgdegeoroc) CMR and C are thesame as in Fig 8 The FOZO and HIMU fields are based on theisotope composition of type islands such as Cook-Austral FOZO andSt Helena (and Cook-Austral HIMU) respectively as reported inStracke et al (2005) The symbols and the error ellipse are the sameas in Fig 5 and 8

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 89

were suggested by the previously estimated P-T conditionsThe calculated degrees of melting (F frac14 38ndash78 for PAC14 and 55ndash113 for PAC21) are on average slightly lowerthan those calculated for alkaline basalts from Hawaii (F frac146ndash11 Zou amp Zindler 1996) SE Australia (F frac14 8ndash13 Zou amp Zindler 1996) and SE China (F frac14 8ndash10 ) On thecontrary the calculated composition of the mantle source ofPachino-Capo Passero rocks (Table 6) is moderatelyenriched with respect to Chondritic values but less so thanthat calculated for Hawaii SE Australia and SE China byroughly a factor 2

The peculiar characteristics of Pachino-Capo Passeromagmas and their mantle sources are evident in Fig 10At comparable BaN (normalized to Primordial Mantlevalues as index of incompatible trace element enrich-ment) the studied Cretaceous rocks have higher TiN andTbYbN than Neogene Hyblean basalts When consideredtogether with the isotope composition the evidence pointsto a mantle source enriched by recycled basaltic oceaniccrust The highly radiogenic Pb isotope ratios (Fig 8 and11) of Pachino-Capo Passero rocks require a history ofhigh time-integrated 238U204Pb 235U204Pb and232Th204Pb The studied rocks do not reach the extremevalues of the end-member HIMU-type island (eg StHelena) but lie just within the isotope range of theFOZO component as recently redefined by Stracke et al(2005)(Fig 11) This component affecting most of OIBhas significantly more radiogenic Pb isotope slightlyhigher 87Sr86Sr and lower 143Nd144Nd than normalupper depleted mantle (eg Depleted MORB Mantle)and it is interpreted as related to the continuous subduc-tion and aging of the basaltic oceanic crust during recy-cling through the mantle Such an explanation can alsoaccount for the high TiO2 contents of the studied rocksPrytulak amp Elliott (2007) demonstrated that the high TiO2

contents of most of OIB worldwide cannot be generatedby either a spinel- or a garnet-lherzolitic mantle evenassuming PM-like TiO2 content for the source Hencethere is a need for a high TiO2 component with the mantlesource of OIB The authors discuss in detail and dismissas potential responsible for the high TiO2 content pro-cesses such as the interaction with Sub-ContinentalLithospheric Mantle suggesting that the most likely com-ponent carrying the high TiO2 signature within the mantleis represented by basaltic oceanic crust recycled aftersubduction in the form of eclogite (Prytulak amp Elliott2007) The TiO2 values of near-primary Pachino-CapoPassero lavas (32 wt for the alkaline group and27 wt for the mildly alkaline one) are among thehighest measured in OIB (Prytulak amp Elliott 2007) mak-ing Pachino ndash Capo Passero along with OIB such as CapeVerde and Canary Islands one of the location where thepresence of the high TiO2 component is most evidentThe same is true for both Pietre Nere and La Quegliasamples showing TiO2 values higher than those ofPachino ndash Capo Passero (35 wt)

A mantle source in which a significant amount ofrecycled basaltic oceanic crust is dispersed within normalslightly depleted peridotitic mantle can therefore explain

the geochemical and isotopic characteristics of the PachinoCapo Passero lavas This is also able to justify the rela-tively high chondrite-normalised TbNYbN of Pachino ndashCapo Passero rocks despite a mantle source mostly withinthe spinel stability field When recycled through subduc-tion processes basaltic oceanic crust undergoes meta-morphism dehydration and melting and it is turned intoeclogite made up by more than 50 of garnet (eg Kesselet al 2005 Klimm et al 2008) The presence of such alithology in the mantle source of Capo Passero magmaseven in small amount (Prytulak amp Elliott 2007 estimates1ndash10 ) would impart a clear garnet signature to theerupted magmas regardless of the type of Al-rich phase(garnet or spinel) in the surrounding normal peridotiteAccordingly the calculated composition of the mantlesource (Table 6) displays higher enrichment of Yb thanfor Tb which is consistent with the presence of garnet

74 Isotope mantle components and implications atregional scale

As highlighted in the introduction a large number ofauthors (eg Worner et al 1986 Wilson amp Downes1991 1992 Cebria amp Wilson 1995 Granet et al 1995Hoernle et al 1995 Wilson amp Patterson 2001 Lustrino ampWilson 2007) have recently suggested the existence of acommon mantle reservoir affecting all the within-platemagmatism of the circum-Mediterranean area related bysome to the up-welling of a deep-seated mantle plume Inthe specific case of southern Italy it is debated whether thegeochemical signature of this asthenospheric componenthas a HIMU-like signature (eg Esperanca amp Crisci 1995Civetta et al 1998 Trua et al 1998 Bianchini et al1999 Gasperini et al 2002 Lustrino amp Wilson 2007) orresembles a common deep-mantle component (Bell et al2004 Cadoux et al 2007) such as FOZO (FOcus ZOneHart et al 1992) or C (Common component Hanan ampGraham 1996) In particular Cadoux et al (2007) excludethe presence of a HIMU end-member beneath southern Italyand suggest that the magmas from Sicily (Sicily ChannelHyblean Etna) represent the deep-seated plume-relatedlsquolsquoCrsquorsquo component Piromallo et al (2008) stand somehowin between these two hypotheses suggesting that the com-mon HIMU-like character found in the alkaline magmatismof the Euro-Mediterranean region is related to a Cretaceouscontamination event linked to the rise of the Central AtlanticPlume (CAP) head which is presently feeding the CanaryIslands This assumption is reached by combining geochem-istry data and palaeogeographic reconstruction showingthat at late Cretaceous-Paleocene time the oldest magmaticcentres of the Euro-Mediterranean region were located morethan 2000 km SW of their present day position in proximityof the CAP hot spot location

The Cretaceous and Paleogene volcanic products ofPachino ndash Capo Passero Pietre Nere and La Quegliarepresent magmatic events close in time to the supposedcontamination event in addition their geographic positionat the moment of eruption was also closer to the present-day

90 R Avanzinelli GT Sapienza S Conticelli

position of the CAP hot spot than most of the other alkalinesuites in Europe These rocks are therefore particularlywell suited to investigate the existence of a Cretaceousplume-related contamination event since their mantlesources should be strongly affected by this process hencedisplaying an isotope composition reflecting that of theCAP hot spot In Fig 8 11 and 12 the isotope compositionof the studied rocks is compared to that of the CanaryIslands (as representative of the CAP) and to the estimatedlsquolsquoCrsquorsquo (Cadoux et al 2007) and CMR components(Lustrino amp Wilson 2007) representing other estimatesof the so-called lsquolsquocommon componentrsquorsquo (Fig 8 11 and12) Fields for oceanic island representing the recently re-defined FOZO (Cook-Austral FOZO islands in Strackeet al (2005)) and the strictly HIMU islands (ie StHelena Cook-Austral Island FOZO in Stracke et al(2005)) are also reported in Fig 11

The Upper Cretaceous and Paleogene rocks fromPachino ndash Capo Passero Pietre Nere and La Queglia plotat the most radiogenic Pb isotope end of the trend definedby the Canary Islands (Fig 8) These compositions are alsomore radiogenic than both the lsquolsquoCrsquorsquo (Cadoux et al 2007)and CMR component (Lustrino amp Wilson 2007) and thanNeogene Hyblean lavas The Sr-Pb isotope composition ofPachino-Capo Passero rocks (Fig 11) represents the closestto typical HIMU islands among all the circum-Mediterranean magmas reported so far (Lustrino ampWilson 2007) They never reach such extreme Pb isotopecomposition but plot well within the field of FOZO islandsas defined by Stracke et al (2005) this composition inter-preted as due to ambient mantle affected by continuous andprolonged subduction of mafic oceanic crust which impartsisotopic signature to the magmas Recycling of mafic ocea-nic crust was also indicated by TiO2 and TbNYbN

The presence of recycled oceanic crust has been alsopostulated for the mantle source of the Canary Islandsthrough different isotope systematics (eg Hoernle ampTilton 1991 Marcantonio et al 1995 Gurenko et al

2009 2010 Day et al 2010 Day amp Hilton 2011) To afirst approximation the isotope composition Pachino-CapoPassero the Neogene Hyblean volcanism and the CanaryIslands could be explained as due to different amounts ofsimilar recycled mafic oceanic crust within the mantlesources of these magmas An increase of this recycledsignature should be favoured by small degrees of partialmelting since eclogitic lithologies are expected to startmelting earlier (eg Prytulak amp Elliott 2007) Pachino-Capo Passero alkali basalts are unlikely to be generated bylower degree of partial melting than basanites and nephe-linites rocks erupted in the Canary Islands and yet theydisplay more radiogenic Pb isotope composition The sameis true when basanites and nephelinites of the NeogeneHyblean plateau are considered

The position of the studied samples with respect to theNHRL (Hart 1984) provides further constraints on the ageand composition of the recycled high 238U204Pb compo-nent In Fig 12 the studied Cretaceous to Paleogene rocksdisplay positive D74 and negative D84 clearly distinctfrom magmas from the Canary Islands which mostly plotin the opposite quadrant Considering that the ambientperidotitic mantle should have isotope compositions simi-lar to the NHRL a shift away from it is indicative of thecontribution of recycled material to the Pb isotope signa-ture of the erupted magmas The variation in D84 is relatedto the time-integrated 232Th238U hence the negative D84of the studied samples indicates mantle sources broadlyenriched in U over Th The shift in D74 is instead indica-tive of time-related variation of 235U238U and it dependson the mean age of the recycled material In Fig 8 wemodelled the Pb isotope composition of a hypothetic maficcrust separated from the mantle at different ages Thecurves are calculated by tracking back in time the averagecomposition of present-day D-DMM mantle source(Workman amp Hart 2005) and assuming that a fractiona-tion event increased the UPb (at various m) at 15 Ga(short-dashed line Fig 8) and 25 Ga (long-dashed line

Table 6 Calculation of partial melting degree and mantle source composition for the Pachino-Capo Passero basalts

Elements bulk D

PAC 14alk

(ppm)

PAC21m alk(ppm) Q

f1 alk

f2m alk Co (Co)N

La 0002 352 234 1504 112 472Ce 0004 715 487 1468 382 554 235 385Nd 0010 386 265 1457 625 901 220 471Sm 0018 779 605 1288 387 561 034 225Tb 0033 109 09 1211 438 631 007 177Yb 0264 166 158 1051 783 1136 049 291Th 0001 335 226 1482 017 597Ce 0004 715 487 1468 596 844 374 611Nd 0010 386 265 1457 749 1070 264 566Sm 0018 779 605 1288 440 621 037 243Tb 0033 109 09 1211 477 673 007 185

Bulk D bulk partition coefficients Q concentration ratio f1 and f2 partial melting degree for PAC 14 and PAC 21 respectively C0 sourceconcentration (C0)N source concentration normalised to chondrite (McDonough amp Sun 1995) Source volume porosity (f frac14 1 ) bulkpartition coefficients and source mineral proportions are the same as those in Table 1 of Zou amp Zindler (1996) La and Th concentration ratio areused as the concentration ratio for the highly incompatible element (Qa) and other REE ratio as the ratio for the less incompatible element (Qb)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 91

Fig 8) respectively generating basaltic oceanic crustwhich then evolved its Pb isotope composition till thepresent day This simple two-stage model is clearly anoversimplification because further events of UPb fractio-nation especially during subduction occur before themafic crust is recycled within the mantle However webelieve it is useful to highlight the need for lsquolsquooldrsquorsquo U-Pbfractionation in order to explain the positive D74 mea-sured in the volcanic rocks of Pachino-Capo Passero PietreNere and most of La Queglia samples whilst the greatmajority of the Canary Islands points toward a lsquolsquoyoungerrsquorsquomodelled crust Further complexity is added by the largevariability of the Pb isotope data of the Canary Islandsreflecting heterogeneous mantle sources and various mantlecomponents Yet it is evident that the components affectingthe mantle source of the Canary Islands and that ofthe Cretaceous Pachino-Capo Passero have differenttime-integrated histories and thus cannot be represented bya single common component It might be argued that the ageand composition of the oceanic crust recycled by the CAP hotspot in the Cretaceous was different from that sampled by thesame hot spot in more recent times during the emplacementof the Canary Islands This hypothesis is not directly testabledue to the lack of Cretaceous products from the CanaryIslands the oldest products of the archipelago for whichisotope data are available (Hoernle amp Tilton 1991 deIgnacio et al 2006) belong from the basal complex ofFuerteventura (20 Ma Balogh et al 1999) These rocksdisplay D74 values among the lowest of all the CanaryIslands (dotted grey squares in Fig 8 and 12) and plotsignificantly away from the Pb isotope composition of thePachino Capo Passero Pietre Nere and La Queglia rocks

Therefore our data show that the mantle sources feedingthe Cretaceous to Paleogene magmatism of southern Italywere significantly different from the CAP hot spot feedingthe Canary Islands Although similar enrichment processesare indicated by geochemical data namely recycling ofsubducted oceanic material the age and composition ofsuch a recycled component appear to be significantly dif-ferent Recycling of subducted mafic crust is widelyaccepted as a process able to affect the composition ofwithin-plate magmas worldwide not only for the extremeHIMU-type islands Stracke et al (2005) pointed out thatextreme HIMU compositions (eg St Helena) are quiteunusual and might require a rare combination of age andcomposition of subduction-modified recycled oceaniccrust On the contrary FOZO compositions such as thatof Pachino-Capo Passero are quite common worldwideThat is not surprising since the process of subduction ofmafic oceanic crust has been long-lived and widespreadthrough the history of the Earth The same conclusion wasreached by Prytulak amp Elliott (2007) who postulated thepresence of mafic oceanic crust at variable extent inalmost any OIB Therefore the presence of recycledmafic crust within the mantle sources of different magmasin a wide area such as the Circum Mediterranean (egLustrino amp Wilson 2007) can hardly be considered as asignificant evidence for a common component In thisstudy we demonstrated that the geochemical characteris-tics of the recycled mafic component in the source of thestudied magmas are not similar to those of similar litholo-gies sampled by the Canary hot spot

Determining whether or not the mafic componentrecycled in the mantle source of Pachino-Capo Passerovolcanic rocks is the same or similar to that present in themantle sources of other circum-Mediterranean magmas is adifficult task given the highly variable isotope compositionand the difficulty to disentangle the various isotope compo-nents in each magmatic suite (eg Lustrino amp Wilson2007) Also within our dataset Pietre Nere and to a lesserextent La Queglia require a high 87Sr86Sr component notconsistent with recycling of MORB-derived eclogitic lithol-ogies A possible explanation may be the interaction withmetasomatised sub-continental lithospheric domains High87Sr86Sr xenoliths from the sub-continental lithosphericmantle beneath Adria have been found within the Neogenemagmatism of Mount Vulture (Downes et al 2002)although the Sr-rich metasomatism may have occurredafter the eruption of Pietre Nere and La Queglia magmas(Downes et al 2002) Similarly a relatively Sr radiogeniccomponent found in Hyblean gabbro xenoliths by Sapienzaet al (2009) has been ascribed to Post-Palaeozoic sub-con-tinental lithospheric domains compatible with a MARID-type reservoir (Sapienza et al 2009)

The alignment of the Pachino-Capo Passero samples inFig 12 might indicate the presence of at least two compo-nents besides the peridotite mantle in the mantle sourcesof these magmas The spread of the data broadly followsthe direction of mass-dependent fractionation indicating apossible effect of a not properly corrected instrumentalmass bias (Fig 12) but the alignment from a component

ndash15 ndash10 ndash5 0 5 10 15

ndash40

ndash20

0

20

40

+ +

+

+

+

+

+

+

++ +

+xxx x

xx

xx

xx

x

xx

xx

x

x

x

xx

Δ74

Δ84

2σ

Fig 12 D74 vs D84 of Pachino-Capo Passero Pietre Nere and LaQueglia volcanic rocks along with literature data for NeogeneHyblean Plateau (Trua et al 1998 Bianchini et al 1999) andCanary Islands (data from the GEOROC database httpgeor-ocmpch-mainzgwdgdegeoroc) Delta values are the differencebetween the Pb isotope ratios of the studied samples and the valuesof the NHRL calculated with the equation of Hart (1984) at thesamplersquos 206Pb204Pb Symbols as in Fig 8 The error ellipse repre-sents the external reproducibility of both the NIST SRM 981 stan-dard (black ellipse) and the AGV1 international rock standard (greyellipse) Symbols and error ellipse as in Fig 5 and 8

92 R Avanzinelli GT Sapienza S Conticelli

position of the CAP hot spot than most of the other alkalinesuites in Europe These rocks are therefore particularlywell suited to investigate the existence of a Cretaceousplume-related contamination event since their mantlesources should be strongly affected by this process hencedisplaying an isotope composition reflecting that of theCAP hot spot In Fig 8 11 and 12 the isotope compositionof the studied rocks is compared to that of the CanaryIslands (as representative of the CAP) and to the estimatedlsquolsquoCrsquorsquo (Cadoux et al 2007) and CMR components(Lustrino amp Wilson 2007) representing other estimatesof the so-called lsquolsquocommon componentrsquorsquo (Fig 8 11 and12) Fields for oceanic island representing the recently re-defined FOZO (Cook-Austral FOZO islands in Strackeet al (2005)) and the strictly HIMU islands (ie StHelena Cook-Austral Island FOZO in Stracke et al(2005)) are also reported in Fig 11

The Upper Cretaceous and Paleogene rocks fromPachino ndash Capo Passero Pietre Nere and La Queglia plotat the most radiogenic Pb isotope end of the trend definedby the Canary Islands (Fig 8) These compositions are alsomore radiogenic than both the lsquolsquoCrsquorsquo (Cadoux et al 2007)and CMR component (Lustrino amp Wilson 2007) and thanNeogene Hyblean lavas The Sr-Pb isotope composition ofPachino-Capo Passero rocks (Fig 11) represents the closestto typical HIMU islands among all the circum-Mediterranean magmas reported so far (Lustrino ampWilson 2007) They never reach such extreme Pb isotopecomposition but plot well within the field of FOZO islandsas defined by Stracke et al (2005) this composition inter-preted as due to ambient mantle affected by continuous andprolonged subduction of mafic oceanic crust which impartsisotopic signature to the magmas Recycling of mafic ocea-nic crust was also indicated by TiO2 and TbNYbN

The presence of recycled oceanic crust has been alsopostulated for the mantle source of the Canary Islandsthrough different isotope systematics (eg Hoernle ampTilton 1991 Marcantonio et al 1995 Gurenko et al

2009 2010 Day et al 2010 Day amp Hilton 2011) To afirst approximation the isotope composition Pachino-CapoPassero the Neogene Hyblean volcanism and the CanaryIslands could be explained as due to different amounts ofsimilar recycled mafic oceanic crust within the mantlesources of these magmas An increase of this recycledsignature should be favoured by small degrees of partialmelting since eclogitic lithologies are expected to startmelting earlier (eg Prytulak amp Elliott 2007) Pachino-Capo Passero alkali basalts are unlikely to be generated bylower degree of partial melting than basanites and nephe-linites rocks erupted in the Canary Islands and yet theydisplay more radiogenic Pb isotope composition The sameis true when basanites and nephelinites of the NeogeneHyblean plateau are considered

The position of the studied samples with respect to theNHRL (Hart 1984) provides further constraints on the ageand composition of the recycled high 238U204Pb compo-nent In Fig 12 the studied Cretaceous to Paleogene rocksdisplay positive D74 and negative D84 clearly distinctfrom magmas from the Canary Islands which mostly plotin the opposite quadrant Considering that the ambientperidotitic mantle should have isotope compositions simi-lar to the NHRL a shift away from it is indicative of thecontribution of recycled material to the Pb isotope signa-ture of the erupted magmas The variation in D84 is relatedto the time-integrated 232Th238U hence the negative D84of the studied samples indicates mantle sources broadlyenriched in U over Th The shift in D74 is instead indica-tive of time-related variation of 235U238U and it dependson the mean age of the recycled material In Fig 8 wemodelled the Pb isotope composition of a hypothetic maficcrust separated from the mantle at different ages Thecurves are calculated by tracking back in time the averagecomposition of present-day D-DMM mantle source(Workman amp Hart 2005) and assuming that a fractiona-tion event increased the UPb (at various m) at 15 Ga(short-dashed line Fig 8) and 25 Ga (long-dashed line

Table 6 Calculation of partial melting degree and mantle source composition for the Pachino-Capo Passero basalts

Elements bulk D

PAC 14alk

(ppm)

PAC21m alk(ppm) Q

f1 alk

f2m alk Co (Co)N

La 0002 352 234 1504 112 472Ce 0004 715 487 1468 382 554 235 385Nd 0010 386 265 1457 625 901 220 471Sm 0018 779 605 1288 387 561 034 225Tb 0033 109 09 1211 438 631 007 177Yb 0264 166 158 1051 783 1136 049 291Th 0001 335 226 1482 017 597Ce 0004 715 487 1468 596 844 374 611Nd 0010 386 265 1457 749 1070 264 566Sm 0018 779 605 1288 440 621 037 243Tb 0033 109 09 1211 477 673 007 185

Bulk D bulk partition coefficients Q concentration ratio f1 and f2 partial melting degree for PAC 14 and PAC 21 respectively C0 sourceconcentration (C0)N source concentration normalised to chondrite (McDonough amp Sun 1995) Source volume porosity (f frac14 1 ) bulkpartition coefficients and source mineral proportions are the same as those in Table 1 of Zou amp Zindler (1996) La and Th concentration ratio areused as the concentration ratio for the highly incompatible element (Qa) and other REE ratio as the ratio for the less incompatible element (Qb)

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 91

Fig 8) respectively generating basaltic oceanic crustwhich then evolved its Pb isotope composition till thepresent day This simple two-stage model is clearly anoversimplification because further events of UPb fractio-nation especially during subduction occur before themafic crust is recycled within the mantle However webelieve it is useful to highlight the need for lsquolsquooldrsquorsquo U-Pbfractionation in order to explain the positive D74 mea-sured in the volcanic rocks of Pachino-Capo Passero PietreNere and most of La Queglia samples whilst the greatmajority of the Canary Islands points toward a lsquolsquoyoungerrsquorsquomodelled crust Further complexity is added by the largevariability of the Pb isotope data of the Canary Islandsreflecting heterogeneous mantle sources and various mantlecomponents Yet it is evident that the components affectingthe mantle source of the Canary Islands and that ofthe Cretaceous Pachino-Capo Passero have differenttime-integrated histories and thus cannot be represented bya single common component It might be argued that the ageand composition of the oceanic crust recycled by the CAP hotspot in the Cretaceous was different from that sampled by thesame hot spot in more recent times during the emplacementof the Canary Islands This hypothesis is not directly testabledue to the lack of Cretaceous products from the CanaryIslands the oldest products of the archipelago for whichisotope data are available (Hoernle amp Tilton 1991 deIgnacio et al 2006) belong from the basal complex ofFuerteventura (20 Ma Balogh et al 1999) These rocksdisplay D74 values among the lowest of all the CanaryIslands (dotted grey squares in Fig 8 and 12) and plotsignificantly away from the Pb isotope composition of thePachino Capo Passero Pietre Nere and La Queglia rocks

Therefore our data show that the mantle sources feedingthe Cretaceous to Paleogene magmatism of southern Italywere significantly different from the CAP hot spot feedingthe Canary Islands Although similar enrichment processesare indicated by geochemical data namely recycling ofsubducted oceanic material the age and composition ofsuch a recycled component appear to be significantly dif-ferent Recycling of subducted mafic crust is widelyaccepted as a process able to affect the composition ofwithin-plate magmas worldwide not only for the extremeHIMU-type islands Stracke et al (2005) pointed out thatextreme HIMU compositions (eg St Helena) are quiteunusual and might require a rare combination of age andcomposition of subduction-modified recycled oceaniccrust On the contrary FOZO compositions such as thatof Pachino-Capo Passero are quite common worldwideThat is not surprising since the process of subduction ofmafic oceanic crust has been long-lived and widespreadthrough the history of the Earth The same conclusion wasreached by Prytulak amp Elliott (2007) who postulated thepresence of mafic oceanic crust at variable extent inalmost any OIB Therefore the presence of recycledmafic crust within the mantle sources of different magmasin a wide area such as the Circum Mediterranean (egLustrino amp Wilson 2007) can hardly be considered as asignificant evidence for a common component In thisstudy we demonstrated that the geochemical characteris-tics of the recycled mafic component in the source of thestudied magmas are not similar to those of similar litholo-gies sampled by the Canary hot spot

Determining whether or not the mafic componentrecycled in the mantle source of Pachino-Capo Passerovolcanic rocks is the same or similar to that present in themantle sources of other circum-Mediterranean magmas is adifficult task given the highly variable isotope compositionand the difficulty to disentangle the various isotope compo-nents in each magmatic suite (eg Lustrino amp Wilson2007) Also within our dataset Pietre Nere and to a lesserextent La Queglia require a high 87Sr86Sr component notconsistent with recycling of MORB-derived eclogitic lithol-ogies A possible explanation may be the interaction withmetasomatised sub-continental lithospheric domains High87Sr86Sr xenoliths from the sub-continental lithosphericmantle beneath Adria have been found within the Neogenemagmatism of Mount Vulture (Downes et al 2002)although the Sr-rich metasomatism may have occurredafter the eruption of Pietre Nere and La Queglia magmas(Downes et al 2002) Similarly a relatively Sr radiogeniccomponent found in Hyblean gabbro xenoliths by Sapienzaet al (2009) has been ascribed to Post-Palaeozoic sub-con-tinental lithospheric domains compatible with a MARID-type reservoir (Sapienza et al 2009)

The alignment of the Pachino-Capo Passero samples inFig 12 might indicate the presence of at least two compo-nents besides the peridotite mantle in the mantle sourcesof these magmas The spread of the data broadly followsthe direction of mass-dependent fractionation indicating apossible effect of a not properly corrected instrumentalmass bias (Fig 12) but the alignment from a component

ndash15 ndash10 ndash5 0 5 10 15

ndash40

ndash20

0

20

40

+ +

+

+

+

+

+

+

++ +

+xxx x

xx

xx

xx

x

xx

xx

x

x

x

xx

Δ74

Δ84

2σ

Fig 12 D74 vs D84 of Pachino-Capo Passero Pietre Nere and LaQueglia volcanic rocks along with literature data for NeogeneHyblean Plateau (Trua et al 1998 Bianchini et al 1999) andCanary Islands (data from the GEOROC database httpgeor-ocmpch-mainzgwdgdegeoroc) Delta values are the differencebetween the Pb isotope ratios of the studied samples and the valuesof the NHRL calculated with the equation of Hart (1984) at thesamplersquos 206Pb204Pb Symbols as in Fig 8 The error ellipse repre-sents the external reproducibility of both the NIST SRM 981 stan-dard (black ellipse) and the AGV1 international rock standard (greyellipse) Symbols and error ellipse as in Fig 5 and 8

92 R Avanzinelli GT Sapienza S Conticelli

Fig 8) respectively generating basaltic oceanic crustwhich then evolved its Pb isotope composition till thepresent day This simple two-stage model is clearly anoversimplification because further events of UPb fractio-nation especially during subduction occur before themafic crust is recycled within the mantle However webelieve it is useful to highlight the need for lsquolsquooldrsquorsquo U-Pbfractionation in order to explain the positive D74 mea-sured in the volcanic rocks of Pachino-Capo Passero PietreNere and most of La Queglia samples whilst the greatmajority of the Canary Islands points toward a lsquolsquoyoungerrsquorsquomodelled crust Further complexity is added by the largevariability of the Pb isotope data of the Canary Islandsreflecting heterogeneous mantle sources and various mantlecomponents Yet it is evident that the components affectingthe mantle source of the Canary Islands and that ofthe Cretaceous Pachino-Capo Passero have differenttime-integrated histories and thus cannot be represented bya single common component It might be argued that the ageand composition of the oceanic crust recycled by the CAP hotspot in the Cretaceous was different from that sampled by thesame hot spot in more recent times during the emplacementof the Canary Islands This hypothesis is not directly testabledue to the lack of Cretaceous products from the CanaryIslands the oldest products of the archipelago for whichisotope data are available (Hoernle amp Tilton 1991 deIgnacio et al 2006) belong from the basal complex ofFuerteventura (20 Ma Balogh et al 1999) These rocksdisplay D74 values among the lowest of all the CanaryIslands (dotted grey squares in Fig 8 and 12) and plotsignificantly away from the Pb isotope composition of thePachino Capo Passero Pietre Nere and La Queglia rocks

Therefore our data show that the mantle sources feedingthe Cretaceous to Paleogene magmatism of southern Italywere significantly different from the CAP hot spot feedingthe Canary Islands Although similar enrichment processesare indicated by geochemical data namely recycling ofsubducted oceanic material the age and composition ofsuch a recycled component appear to be significantly dif-ferent Recycling of subducted mafic crust is widelyaccepted as a process able to affect the composition ofwithin-plate magmas worldwide not only for the extremeHIMU-type islands Stracke et al (2005) pointed out thatextreme HIMU compositions (eg St Helena) are quiteunusual and might require a rare combination of age andcomposition of subduction-modified recycled oceaniccrust On the contrary FOZO compositions such as thatof Pachino-Capo Passero are quite common worldwideThat is not surprising since the process of subduction ofmafic oceanic crust has been long-lived and widespreadthrough the history of the Earth The same conclusion wasreached by Prytulak amp Elliott (2007) who postulated thepresence of mafic oceanic crust at variable extent inalmost any OIB Therefore the presence of recycledmafic crust within the mantle sources of different magmasin a wide area such as the Circum Mediterranean (egLustrino amp Wilson 2007) can hardly be considered as asignificant evidence for a common component In thisstudy we demonstrated that the geochemical characteris-tics of the recycled mafic component in the source of thestudied magmas are not similar to those of similar litholo-gies sampled by the Canary hot spot

Determining whether or not the mafic componentrecycled in the mantle source of Pachino-Capo Passerovolcanic rocks is the same or similar to that present in themantle sources of other circum-Mediterranean magmas is adifficult task given the highly variable isotope compositionand the difficulty to disentangle the various isotope compo-nents in each magmatic suite (eg Lustrino amp Wilson2007) Also within our dataset Pietre Nere and to a lesserextent La Queglia require a high 87Sr86Sr component notconsistent with recycling of MORB-derived eclogitic lithol-ogies A possible explanation may be the interaction withmetasomatised sub-continental lithospheric domains High87Sr86Sr xenoliths from the sub-continental lithosphericmantle beneath Adria have been found within the Neogenemagmatism of Mount Vulture (Downes et al 2002)although the Sr-rich metasomatism may have occurredafter the eruption of Pietre Nere and La Queglia magmas(Downes et al 2002) Similarly a relatively Sr radiogeniccomponent found in Hyblean gabbro xenoliths by Sapienzaet al (2009) has been ascribed to Post-Palaeozoic sub-con-tinental lithospheric domains compatible with a MARID-type reservoir (Sapienza et al 2009)

The alignment of the Pachino-Capo Passero samples inFig 12 might indicate the presence of at least two compo-nents besides the peridotite mantle in the mantle sourcesof these magmas The spread of the data broadly followsthe direction of mass-dependent fractionation indicating apossible effect of a not properly corrected instrumentalmass bias (Fig 12) but the alignment from a component

ndash15 ndash10 ndash5 0 5 10 15

ndash40

ndash20

0

20

40

+ +

+

+

+

+

+

+

++ +

+xxx x

xx

xx

xx

x

xx

xx

x

x

x

xx

Δ74

Δ84

2σ

Fig 12 D74 vs D84 of Pachino-Capo Passero Pietre Nere and LaQueglia volcanic rocks along with literature data for NeogeneHyblean Plateau (Trua et al 1998 Bianchini et al 1999) andCanary Islands (data from the GEOROC database httpgeor-ocmpch-mainzgwdgdegeoroc) Delta values are the differencebetween the Pb isotope ratios of the studied samples and the valuesof the NHRL calculated with the equation of Hart (1984) at thesamplersquos 206Pb204Pb Symbols as in Fig 8 The error ellipse repre-sents the external reproducibility of both the NIST SRM 981 stan-dard (black ellipse) and the AGV1 international rock standard (greyellipse) Symbols and error ellipse as in Fig 5 and 8

92 R Avanzinelli GT Sapienza S Conticelli

with positive D74 and D840 to another one with nega-tive D84 and D74 0 appear to be well beyond theexternal reproducibility of the measured international stan-dards (ie AGV1) These two components however arenot evidenced by any geochemical data other than Pbisotopes which indeed do not correlate with other isotopeor key trace-element ratios (eg BaCe BaNb NbU CePb and SrNb) For example a positive correlation betweenthe D74 and 87Sr86Sr not observed should be expected ifthe positive D74 was related to the radiogenic Sr compo-nent found at Pietre Nere that also plot at similar deltavalues The lack of other geochemical evidences suggeststhat both components might be related to the recycling ofmafic oceanic crusts but with variable age (older for thepositive D74 component) and UTh

In summary we do not find at least from a geochemicalpoint of view the need for a single original reservoir for acommon component linking Pachino-Capo Passero magmasto those from a wide range of location from Central andSouthern Europe In particular Pb isotope data seem toexclude a direct connection between the mantle source ofthe studied samples and a deep-seated mantle plume similarto that feeding the Canary Islands (Piromallo et al 2008)Indeed we agree with the suggestion by Lustrino amp Wilson(2007 and reference therein) that mantle melting is likely tobe related to passive upwelling of asthenospheric mantlerelated to an episode of extensional tectonics occurringduring the rotation and convergence of Africa and Eurasia

8 Conclusions

This study provides insights on the petrogenesis ofCretaceous and Paleogene volcanics from Pachino-CapoPassero Pietre Nere and Mt La Queglia in the frame of thedebated geochemical and isotopic signature of the CentralMediterranean area

The Pachino-Capo Passero volcanic rocks display typi-cal within-plate compositions little affected by crustal con-tamination processes thus representing near-primarymagma composition The evidence for cumulus and frac-tionation of mainly mafic phases suggests the presence of ashallow reservoir although the storage was not prolonged

The studied lavas belong to two different groups analkaline and a mildly alkaline one originated at differentdegrees of partial melting with the former appearing to begenerated from a slightly deeper and hotter mantle sourceThe magmas originated from an asthenospheric upper man-tle probably still within the spinel stability field This rela-tively shallow origin suggests that melting occurred inrelationship to passive upwelling in response to lithosphericstretching in extensional tectonic settings The CretaceousPachino-Capo Passero rocks originated from a mantlesource distinct from that of the neighbouring NeogeneHyblean volcanic products in terms of depth degree oftrace-element depletion and also palaeogeographic location

The high radiogenic Pb isotope ratio anomalously highTiO2 contents and MREEHREE ratios of Capo-Passero

Pachino rocks indicate the presence of high-Ti garnet-richeclogitic lithologies within the mantle sources Theselithologies derive from the subduction and recycling ofmafic oceanic crust which evolved at high m (238U204Pb)and low k (232Th238U) for considerable time before beingsampled by magmatism A similar component is present inthe mantle source of La Queglia and Pietre Nere magmaswhich are also affected by a radiogenic Sr componentpossibly related to interaction with enriched sub-continen-tal lithospheric mantle

The studied Cretaceous to Paleogene rocks are well suitedto investigate the presence of the common asthenosphericcomponent variously claimed for the magmatism of theCentral Mediterranean region Their isotopic compositionlies just outside the Common Mantle Reservoir field ofLustrino amp Wilson (2007) towards HIMU-like end-membersIn fact the isotope composition of the studied magmas fallswell within the field of the recently re-defined FOZO com-ponent of Stracke et al (2005) This is perfectly consistentwith its derivation from a mantle continuously modified byprolonged subduction and aging of mafic oceanic crust(Stracke et al 2005) The extremely widespread nature ofthis process well explains its almost ubiquitous presenceworldwide (eg Stracke et al 2005 Prytulak amp Elliott2007) In this context we do not find any need for a uniquereservoir responsible for this isotopic signature such as thepresence of a HIMU-like or FOZO-like deep-seated plumeMoreover the comparison of the geochemical and isotopecomposition of the studied rocks volcanic rocks with that ofmagmas from the Canary Islands shows that the maficrecycled components required by the geochemical and iso-topic composition of both magmatic suites have distinctlydifferent isotope composition and time-integrated historyThese data are evidence against any connection between themantle source of the studied magmas and a possible contam-ination event related to the Central Atlantic Plume (CAP)

Acknowledgements The authors wish to thank ElenaBoari Chiara Petrone Maurizio Ulivi and SimoneTommasini for their invaluable assistance during dataacquisition Nicoletta Mirco for providing Pietre Neresamples and Julie Prytulak for stimulating discussionsThe manuscript was greatly improved by constructiveand thoughtful reviews by Nick Rogers and LuigiBeccaluva Funding for this research was provided byPRIN_2008 (grant 2008HMHYFP_002) and MIURlsquolsquoRientro dei cervellirsquorsquo Programme

References

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Amore C Carveni P Scribano V Sturiale C (1988) Facies ed

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The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 93

Arisi Rota F amp Fichera R (1987) Magnetic interpretation related

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Tectonophysics 138 179ndash196

Avanzinelli R Bindi L Menchetti S Conticelli S (2004)

Crystallisation condition and genesis of peralkaline magmas

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Avanzinelli R Boari E Conticelli S Francalanci L Guarnieri

L Perini G Petrone CM Tommasini S Ulivi M (2005)

High precision Sr Nd and Pb isotopic analyses using the new

generation Thermal Ionisation Mass Spectrometer

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Balogh K Ahijado A Casillas R Fernandez C (1999)

Contributions to the chronology of the basal complex of

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Barberi F Civetta L Gasparini P Innocenti F Scandone R

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plate-boundary paleomagnetic and volcanological evidence

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Macciotta G Tassinari R Vaccaro C (1998) Nephelinitic to

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Beccaluva L Bianchini G Bonadiman C Coltorti M Milani

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nephelinite to tholeiite magma generation in the Paleogene

Veneto volcanic province southern Alps in lsquolsquoCenozoic

Volcanism in the Mediterranean Arearsquorsquo L Beccaluva G

Bianchini M Wilson eds Geological Society of America

Boulder CO Special Paper 418 131ndash152

Beccaluva L Bianchini G Ellam RM Marzola M Oun KM

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components in the North African lithospheric mantle petrolo-

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of London London Special Publications 253ndash277

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narrow whole mantle plume below Iceland Earth Planet Sci

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Boari E amp Conticelli S (2007) Mineralogy and Petrology of Mg-

rich calc-alkalic potassic and ultrapotassic associated rocks the

Middle Latin Valley monogenetic volcanoes Roman Magmatic

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unique lower mantle source for Southern Italy volcanics Earth

Planet Sci Lett 259 227ndash238

Carbone S amp Lentini F (1981) Caratteri deposizionali delle vul-

caniti del Miocene superiore negli Iblei (Sicilia sud-orientale)

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Carbone S Grasso M Lentini F (1982) Considerazioni sullrsquoe-

voluzione geodinamica della Sicilia Sud-Orientale dal Cretaceo

al Quaternario Mem Soc Geol Ital 24 367ndash386

Carter SR amp Civetta L (1977) Genetic implications of the isotope

and trace element variations in the eastern Sicilian volcanics

Earth Planet Sci Lett 36 168ndash180

Carveni P Romano R Capodicasa A Tricomi R (1991)

Geologia dellrsquoarea vulcanica di Capo Passero (Sicilia sud-orien-

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Cebria JM amp Wilson M (1995) Cenozoic mafic magmatism in

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Civetta L DlsquoAntonio M Orsi G Tilton GR (1998) The geo-

chemistry of volcanic rocks from Pantelleria Island Sicily

Channel petrogenesis and characteristics of the mantle source

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Conticelli S DlsquoAntonio M Pinarelli L Civetta L (2002)

Source contamination and mantle heterogeneity in the genesis

of Italian potassic and ultrapotassic volcanic rocks Sr-Nd-Pb

Isotope data from Roman Province and Southern Tuscany

Mineral Petrol 74 189ndash222

Conticelli S Carlson RW Widom E Serri G (2007) Chemical

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Arearsquorsquo L Beccaluva G Bianchini M Wilson eds Geological

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Conticelli S Laurenzi MA Giordano G Mattei M

Avanzinelli R Melluso L Tommasini S Boari E Cifelli

F Perini G (2010) Leucite-bearing (kamafugiticleucititic)

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superiore nel sottosuolo di Ragusa (Sicilia sud-orientale)

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Day JMD amp Hilton DR (2011) Origin of 3He4He ratios in

HIMU-type basalts constrained from Canary Island lavas

Earth Planet Sci Lett 305 226ndash234

Day JMD Pearson DG Macpherson CG Lowry D

Carracedo J-C (2010) Evidence for distinct proportions of

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de Ignacio C Munoz M Sagredo J Fernandez-Santin S

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component of the alkaline-carbonatite association of

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DePaolo DJ (1988) Nd Isotope Geochemistry An Introduction

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Dewey JF Helman ML Turco E Hutton DHW Knott SD

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Tectonicsrsquorsquo MP Coward D Dietrich RG Park eds

Geological Society of London London Special Publications

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Downes H Kostoula T Jones AP Beard AD Thirlwall M

Bodinier J-L (2002) Geochemistry and SrndashNd isotopic com-

positions of mantle xenoliths from the Monte Vulture carbona-

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Durazzo A Taylor LA Shervais JW (1984) Ultramaphic lam-

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for the development of DMM-HIMU isotopic compositions in a

long-lived extensional setting Earth Planet Sci Lett 136

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Faccenna C Jolivet L Piromallo C Morelli A (2003)

Subduction and the depth of convection in the Mediterrranean

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Frey FA Garcia MO Wise WS Kennedy A Gurriet P

Albarede F (1991) The evolution of Mauna Kea volcano

Hawaii petrogenesis of tholeiitic and alkalic basalts J

Geophys Res 96 14347ndash14375

Frey FA Green DH Roy SD (1978) Integrated model of basalt

petrogenesis a study of quartz tholeiites to olivine melilitites

from South Eastern Australia utilizing geochemical and experi-

mental data J Petrol 19 463ndash 513

Gasperini D Blichert-Toft J Bosch D Del Moro A Macera P

Albarede F (2002) Upwelling of deep mantle material through

a plate window evidence from the geochemistry of Italian

basaltic volcanics J Geophys Res 107 2367ndash2386

George R Rogers N Kelley S (1998) Earliest magmatism in

Ethiopia evidence for two mantle plumes in one flood basalt

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Goes S Spakman W Bijwaard H (1999) A lower mantle source

for Central European Volcanism Science 286 1928ndash1931

Granet M Wilson M Achauer U (1995) Imaging a mantle

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Gurenko AA Sobolev AV Hoernle K Hauff F Schmincke

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Earth Planet Sci Lett 277 514ndash524

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(Canary Islands) shield stage magmas evidence from olivine

composition and Sr-Nd-Pb isotopes Contrib Mineral Petrol

159 689ndash702

Halliday AN Lee D-C Tommasini S Davies GR Paslick

CR Fitton JG James DE (1995) Incompatible trace ele-

ments in OIB and MORB and source enrichment in the sub-

oceanic mantle Earth Planet Sci Lett 133 379ndash395

Hanan BB amp Graham DW (1996) Lead and helium isotope

evidence from oceanic basalts for a common deep source of

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Hart SR (1984) A large-scale isotope anomaly in the Southern

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Hart SR Hauri EH Oschmann LA Whitehead JA (1992)

Mantle plumes and entrainment - Isotopic evidence Science

256 517ndash520

Hoernle K Zhang Y-S Graham D (1995) Seismic and geochem-

ical evidence for large-scale mantle upwelling beneath the eastern

Atlantic and western and central Europe Nature 374 34ndash39

Hoernle KA amp Tilton GR (1991) Sr-Nd-Pb isotope data for

Fuerteventura (Canary Islands) Basal Complex and subaerial

volcanics application to magma genesis and evolution

Schweiz Mineral Petrogr Mitt 61 3ndash18

Irvine TN amp Baragar WRA (1971) A guide to chemical classi-

fication of common ingeneous rocks Can J Earth Sci 8

523ndash548

Kessel R Schmidt MW Ulmer P Pettke T (2005) Trace

element signature of subduction-zone fluids melts and super-

critical liquids at 120ndash180 km depth Nature 437 724ndash727

Klein EM amp Langmuir CH (1987) Global correlation of ocean

ridge basalt chemistry with axial depth and crustal thickness J

Geophys Res 92 8089ndash8115

Klimm K Blundy JD Green TH (2008) Trace element parti-

tioning and accessory phase saturation during H2O-saturated

melting of basalt with implications for Subduction zone chemi-

cal fluxes J Petrol 49 523ndash553

Le Bas MJ Le Maitre RW Streckeisen A Zanettin B (1986)

A chemical classification of volcanic rocks based on the Total

Alkali-Silica diagram J Petrol 27 745ndash750

Lentini F Carbone S Catalano S Grasso M (1996) Elementi

per la ricostruzione del quadro strutturale della Sicilia orientale

Mem Soc Geol Ital 51 179ndash195

Longaretti G amp Rocchi S (1990) Il magmatismo dellrsquoAvampaese

Ibleo (Sicilia Orientale) tra il Trias e il Quaternario dati strati-

grafici e petrologici di sottosuolo Mem Soc Geol Ital 45

911ndash925

Lustrino M amp Wilson M (2007) The circum-Mediterranean anoro-

genic Cenozoic igneous province Earth Sci Rev 81 1ndash65

Marcantonio F Zindler A Elliott T Staudigel H (1995) Os

isotope systematics of La Palma Canary Islands evidence for

recycled crust in the mantle source of HIMU ocean islands

Earth Planet Sci Lett 133 397ndash410

McDonough WF amp Sun SS (1995) The composition of the

Earth Chem Geol 120 223ndash253

The Cretaceous to Paleogene within-plate magmatism of Pachino-Capo Passero and Adria 95

McKenzie D amp OrsquoNions RK (1991) Partial melt distributions

from inversion of rare earth element concentrations J Petrol

32 1021ndash1091

Morimoto N (1988) Nomenclature of pyroxenes Fortschr

Mineral 66 237ndash252

OrsquoConnor JM Stoffers P van den Boogard P McWilliams M

(1999) First seamount age evidence for significantly slower

African plate motion since 19ndash30 Ma Earth Planet Sci Lett

171 575ndash589

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Opening of the Central Atlantic and asymmetric mantle upwel-

ling phenomena implications for long-lived magmatism in wes-

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Patacca E Scandone P Giunta G Liguori V (1979) Mesozoic

paleotectonic evolution of the Ragusa zone (Southeastern

Sicily) Geol Rom 18 331ndash369

Perini G amp Conticelli S (2002) Crystallization conditions of

Leucite-Bearing magmas and their implications on the magma-

tological evolution of ultrapotassic magmas the Vico Volcano

Central Italy Mineral Petrol 74 253ndash276

Piromallo C Gasperini D Macera P Faccenna C (2008) A late

Cretaceous contamination episode of the

EuropeanndashMediterranean mantle Earth Planet Sci Lett 268

15ndash27

Prytulak J amp Elliott T (2007) TiO2 enrichment in ocean island

basalts Earth Planet Sci Lett 263 388ndash403

Rocchi S Longaretti G Salvadori M (1998) Subsurface

Mesozoic and Cenozoic magmatism in south-eastern Sicily

distribution volume and geochemistry magmas Acta

Vulcanol 10 395ndash408

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Sapienza G amp Scribano V (2000) Distribution and representative

whole-rock chemistry of deep-seated xenoliths from the Iblean

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185ndash204

Sapienza GT Griffin WL OlsquoReilly SY Morten L (2007)

Crustal zircons and mantle sulfides Archean to Triassic events

in the lithosphere beneath south-eastern Sicily Lithos 96

503ndash523

mdash mdash mdash mdash (2009) Petrology and Sr-Nd-Hf isotope geochemistry

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Scarascia S Lozej A Cassinis R (1994) Crustal structures of the

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Scribano V Sapienza G Braga R Morten L (2006) Gabbroic

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Geochim Cosmochim Acta 34 237ndash243

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Stracke A Hofmann AW Hart SR (2005) FOZO HIMU and

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Sun SS amp McDonough WF (1989) Chemical and isotopic sys-

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Saunders amp MJ Norry eds Geological Society of London

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Thirlwall M (2000) Inter-laboratory and other error in Pb isotope

analyses investigated using a 207Pb-204Pb double spike Chem

Geol 163 299ndash322

Tonarini S DlsquoOrazio M Armienti P Innocenti F Scribano V

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Trua T Esperanca S Mazzuoli R (1998) The evolution of the

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Vichi G Stoppa F Wall F (2004) The carbonate fraction in

carbonatitic Italian lamprophyres Lithos 85 154ndash170

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Geosyst 7 Q08006 doi1010292006GC001283

Wilson M amp Downes H (1991) TertiaryndashQuaternary extension-

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mdash mdash (1992) Mafic alkaline magmatism associated with the

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Geological Society of America Boulder CO Special Paper

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Chem Geol 171 33ndash47

Received 17 December 2010

Modified version received 15 September 2011

Accepted 4 November 2011

96 R Avanzinelli GT Sapienza S Conticelli