Regional variations within the Paraná flood basalts (southern Brazil): Evidence for subcontinental mantle heterogeneity and crustal contamination

Chemical Geology', 75 (1989) 103-122 103 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

[1]

REGIONAL VARIATIONS WITHIN THE PARANA FLOOD BASALTS (SOUTHERN BRAZIL): EVIDENCE FOR

SUBCONTINENTAL MANTLE HETEROGENEITY AND CRUSTAL CONTAMINATION

E.M. PICCIRILLO 1, L. CIVETTA 2, R. PETRINI 3, A. LONGINELLI 1, G. BELLIENI 4, P. COMIN-CHIARAMONTI s, L.S. MARQUES s and A.J. M E L F P

~ Istituto di Mineralogia e Petrografia, University of Trieste, Trieste (Italy') ~Dipartimento di Geofisica e Vulcanologia, University of Napoli, Napoli (Italy')

:Tstituto di Geocronologia e Geochimica Isotopica, Consiglio Nazionale deUe Ricerche, Pisa (Italy) 4Dipartimento di Mineralogia e Petrologia, University of Padova, Padova (Italy)

';Istituto di Mineralogia, Petrografia e Geochimica, University of Palermo, Palermo (Italy') ~Tnstituto Astronomico e Geofisico, University o[ Sgto Paulo, Silo Paulo (Brazil)

(Received October 26, 1987; revised and accepted September 6, 1988)

Abstract

Piccirillo, E.M., Civetta, L., Petrini, R., Longinelli, A., Bellieni, G., Comin-Chiaramonti, P., Marques, L.S. and Melfi, A.J., 1989. Regional variations within the Parand flood basalts (southern Brazil): Evidence for subcontinental mantle heterogeneity and crustal contamination. Chem. Geol., 75: 103-122.

Continental flood volcanism of the Parand basin (Lower Cretaceous) is represented by two-pyroxene tholeiitic basalts (90 vol. % ). The Northern ParanA Province (NPP) is dominated by basalts high in TiO~ and incompatible elements (HTiB), while the Southern Paran~ Province (SPP) is dominated by basalts low in TiO~ and incompatible elements (LTiB).

NPP basalts show relatively small variations of initial (120 Ma) 87Sr/~SSr (Ro) and l~:~Nd/~44Nd (Nd*) ratios (R,,=0.7051-0.7062 and Nd*=0.5124-0.5125, respectively) relative to those occurring in SPP (R~,=0.7046-0.7120 and Nd* = 0.5122-0.5128, respectively ). The latter basalts show significant positive correlations between R,} vs. SiO2, K,O, Rb and Ba, and negative correlations between Ro vs. (Cr+Ni) and mg-value, believed to be due to crustal "granitic" contamination. In general, the effects of contamination are pronounced in SPP and tend to vanish towards NPP. 5 ~SO-values range from + 6.5 to + 10.09~ in the basalts from NPP and SPP and essentially reflect water-magma interactions.

"Uncontaminated" LTiB and HTiB basalts from NPP are isotopically distinct from the "uncontaminated" analogues from SPP (LTiB) (Ro = 0.7055 vs. 0.7046; Nd* = 0.5124 vs. 0.5128, respectively). All chemical data consistently indicate distinct sources and a large-scale mantle heterogeneity. The NPP mantle source is expected to have relatively high content of "enriched" components, possibly related to small-volume melts and metasomatic fluids. Tentatively, the last stabilization age of the Parand mantle heterogeneity is 0.5-1.0 Ga old.

The existence of high- and low-TiO2 basalt suites in both Paran~i and Karoo provinces in Brazil and southern Africa, respectively, indicates a large-scale heterogeneity in the subcontinental mantle, and suggests that basalt generation occurred in the lithospheric mantle.

0009-2541/89/$03.50 © 1989 Elsevier Science Publishers B.V.

104

1. Introduction

The study of flood continental basalts is important for evaluating the composition of the mantle source (s) from which they are derived, provided the basalts represent primitive magmas not modified by interaction with crustal material.

An important petrological problem concerns the degree to which the continental basalts are crustally contaminated, or derive their geochemical features from more or less enriched mantle affected by metasomatic processes (e.g., Hawkesworth et al., 1984).

Most continental flood basalts are not primary melts, but have undergone significant fractional crystallization (e.g., Cox, 1980) between the "base of continental crust and near surface" (Thompson et al., 1983). Thus it is possible that some geochemical features (e.g., high STSrff6Sr ratios, K20 and SiO~) may be related to the assimilation of crustal components during fractional crystallization (e.g., DePaolo, 1981 ). Moreover, crustal contamination may be related to assimilation/equilibrium crystallization (Devey and Cox, 1987), or to several other mixing mechanisms which are de- pending on the initial magma temperature, the flow rate, temperature, composition and distribution of rock types in the crust, and the magma composition (el. Huppert and Sparks, 1985).

The evaluation of crustal contaminat ion in the basalt petrogenesis is therefore essential in order to estimate the geochemical features of the source material(s) (e.g., Thompson et al., 1983: Cox and Hawkesworth, 1984). This can allow us to evaluate whether the continental flood basalts were derived from the lithospheric and/or asthenospheric mantle (e.g., Cox, 1987) and elucidate the role of mantle metasomatic processes including those involving continental material recycled into the upper mantle by sub- duction (e.g., Weaver and Tarney, 1983).

The present study addresses the flood basalts of the Paranfi basin which have important chemical and systematic variations. It will be

shown that part of the chemical and isotopic characteristics are related to different mantle sources, while others are essentially the result of variable degrees of crustal contamination. A detailed discussion of basalt chemistry result- ing from different degrees of melting of a homogeneous source will be presented elsewhere (Piccirillo et al., 1988b. ).

2. Geological notes and geochemical provinces

The continental flood volcanics of the Par- an~i basin are of Early Cretaceous age ( 140-120 Ma) and cover an area of 1.2.10 ~ km 2 (volume ~ 0.79.106 km :~ ).

The volcanics (Fig. 1) are dominantly tholeiites (90 vol.%) with subordinate tholeiitic andesites (7 vol.%) and rhyodacites to rhyo- lites (3 vol.% ).

Geological and geochemical data (Bellieni et al., 1984a,b,c, 1986a,b; Piccirillo et al., 1987, 1988a) can be used to divide the Paran~i basin into two main provinces (Fig. 1 ): (A) Southern Paranfi Province (SPP, region south of the Rio Uruguay lineament and part of that between the Rio Piquiri and Rio Uruguay l ineaments); and (B) Northern Paran~i Province (NPP, region north of the Rio Piquiri l ineament and part of that between the Rio Piquiri and Rio Uruguay l ineaments) .

In SPP the earlier volcanics are tholeiitic basalts (70 vol.% ), while the most recent ones are largely represented by laterally persistent sheet- like rhyodacitic to rhyolitic flows (Palmas type; 13 vol.% ) with minor intercalations of tholeiitic basalts and andesites. The latter ( 17 vol.% ) tend to be more concentrated between the lower (basic) and upper (acid) parts of the suite. The Palmas acid volcanics are concentrated in the eastern parts of SPP, and reach their maximum thickness (400 m) in the southeast (Fig. 1).

NPP is characterized by tholeiites which, in the southeasternmost regions, are overlain by minor (1 vol.%) sheet-like rhyodacitic to rhyolitic flows (Chapecd type) with a maxi-

56 + 5 2 + 50 °

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+

+ +

-6

6 + + + + +

+/' + 4- + / ~ + + -6

+ +

j + + -6 -6 -6

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105

~0 °

. " .x J ~ . . - " '

÷

+ +

-6 +

+

A

A f-

q~

,X A

3T

58+ 56 ° 54 ° 5T 50 ~ ~,B °

Fig. 1. Simplified geological sketch-map of Parand basin (after Petr in i et al,, 1987). 1 =pre -Devon ian crystalline basement; 2=pre-volcanic sediments (mainly Paleozoic); 3 = b a s i c to in termediate flood volcanics (Serra Geral Formation: Lower Cretaceous); 4 = acid stratoid volcanics: Palmas type (Serra Geral Format ion) ; 5 = acid stratoid voleanics: Chapec6 type (Serra Geral Format ion ); 6 --- post-volcanic sediments (mainly Upper Cretaceous); 7-= arch-type structure; 8 -- tectonic and / or magnetic l ineament; 9 = sample location: present paper and Petr in i et al. ( 1987 ); triangles = low-TiO:~ basal ts /andesi tes : solid circles = high-TiO._, basalts.

106

TABLEI

Average major- (wt.%) and trace- (ppm) element compositions of low- ( <2 wt.% ) and high-Ti02 ( > 2 wt.% ) basalts with MgO = 4-5 wt.% from the southern ($1 and $2) and northern (NI to N3) Paran~ basin

S ] S 2 N 1 N 2 N 3

a v e r . N a v e r . N a v e r , N a v e r . N a v e r . N

S i ( 9 3 . 5 9 ~42 % ; , 9 7 : 5] .62 5 5 ] . 2 t , ]22 f , 1 . ; a ~:,

T~, 1 . 5 3 l a ; < [ 5 , 1 . 9 2 5 P , 8 7 127 3 . 5 0 37

A1 ) 14191 ] 4 2 I ] . 8 ] 5 1 5 . 2 1 5 ! 4 , 1 1 ] 2 [ ~ ] ] i 6 9 3:' 2

F~,>+ 1 1 . 5 5 142 I 1 , ' ] 2 , 12 . , 19 5 1 3 , 2 9 ] 2 2 ! 3 . 5 6 ~1'

b~n:) ) , ? 0 ] 4 2 . ] 6 % 0 . 2 2 5 c , , 2 l ] 2 ' 0 . 2 0 ~:'

Mg,2 a . 6 1 142 4 . 4 ; ' , z~.6~ 5 4 , 6 5 122 z1 .46 y:'

Ca0 9 . ) 1 142 ~ , 4 8 5 1 0 . 0 3 5 9,17 122 & , ¢ % ~1'

Na£ H 1 , , ' ~ ] 4 2 ' , 6 7 % 2 .L :9 5 2 , 7 : I P 2 , , 7 4 3?

K 2 0 ] , ' 8 / 4 1 / , 8 3 5 C' .9C 5 1 , 2 9 122 1 . ,15 ~1'

~ 2 " 5 0 . , 4 1A2 S . 6 4 ', 0 , 3 4 5 ( , 4 3 122 O , A ~:'

I j 1.,36 3C :1:.:~i % 0 , 3 4 5 C , 6 8 11 O , ? i T

Th 4 . 6 2 3 0 4 . 1 6 b 2 , 1 1 5 3 , ] 0 11 3 . 2 2 1'

C r 50 142 6 2 h 39 5 8 2 12~ 4 7 17

N : 4 9 142 [ 5 ', 6 8 5 %6 122' 4 4 t i '

Ba 366 1 4 2 6 6 ? 5 38C, 5 5 0 6 1 2 2 6 1 7 E '

Rb 4 ] 142 ~ ;, 17 5 2 8 1 2 2 3 ] ~','

S r 2 2 9 1 4 2 6 ~ . [ 2 9 8 5 411 1 2 2 b o a %7

La 2 2 1 4 2 4 5 19 5 32 122 ~;'

C~ 52 ],~2 ~7 b 53 5 7 4 1 2 2 8 8 31'

Zr ] 4 4 1 4 2 2 % t 12.6 5 2 1 6 1 2 2 2C2 3 : '

Y 32 1 4 2 32 5 30 5 3 4 1 2 2 : 4 37

[87SF/86Sr) C,70866 23 ),70598 7 C.70578 5 0.70572 ]6 0.70565 9 o

(I43Nd/]44Nd) 0,51234 ]0 0.5]236 2 0.51248 2 0.51~42 8 0.%12a4 , m

Major-element contents recalculated to 100 wt.% on a volatile-free basis. N--number of samples. Chemical constraints for sample selection: MgO =4-5 wt.%, SiO~ < 55 wt.%, loss on ignition <2 wt.% and TiOe<2 wt.% for $1 and N1, TiO~> 2 wt.% for $2 and N2, and TiO~> 3 wt.% for N3. (STSrff~Sr)o = computed back to 120 Ma; ( '4:~Nd/ "~Nd ) m = measured value. Source isotope data: Fodor et al. (1985); Mantovani et al. (1985a); Hawkesworth et al. (1986); Petrini et al. (1987); Piccirillo et al. (1987) and present study.

mum thickness of 200 m. Locally, Chapec5 acid volcanics have intercalations of, or are overlain by 20-200-m-thick tholeiitic basalts. Interme- diate rock types are virtually absent.

In SPP the basalts are dominantly (93 vol.% ) low in T i Q ( < 2 wt.%; av. 1.48 + 0.24 wt.% ) and incompatible elements (LTiB), while in NPP most of the basalts (94 vol.% ) h a v e high contents of TiO2 ( > 2 wt.%; av. 3.03 +0.21 wt.% ) and incompatible elements (HTiB) .

In general, LTiB are depleted in Ba, La, Ce, Zr and Sr relative to HTiB for equal MgO (Ta- ble I). However, LTiB from southern Parang have, on average, higher Rb, U and Th relative to HTiB, as well as higher values of STSr/S6Sr initial ratio (R0) and lower 143Nd/]44Nd ratios (Table I). These chemical and isotopic differences are also shared by Palmas (low in incompatible elements ) and Chapec6 (high in incompatible elements) acid volcanics (Fodor et al., 1985; Mantovani et al., 1985a, b; Bellieni et al., 1986b; Piccirillo et al., 1987; L.S. Marques and Molina, unpublished data, 1988). It should be noted that the volcanics low in incompatible elements (LTiB and Palmas) dominate in SPP, while those high in incompatible elements (HTiB and Chapec6) prevail in NPP.

3. Sample selection and petrographic notes

The basaltic and andesitic specimens were selected from a collection of ~ 1200 samples and are believed to be representative of the different low- and high-TiO,~ volcanics in the northern and southern Paran4 provinces.

Most of the samples have phenocrystal { 0.5- 2 mm) contents of < 10 vol.%. Their classification and essential mineral assemblages are given in the Appendix.

Basaltic rock types (LTiB and HTiB) usually contain phenocrysts and/or micropheno- crysts (0.2-0.5 mm) of augite (W04~ ~) , plagioclase (Ansi_45) , pigeonite (W012 ~), minor Ti-magnetite (ilmenite) and sporadic olivine, the latter completely altered. Plagioclase, augite, pigeonite, abundant Ti-magnetite and ilmenite commonly make up the groundmass.

Intermediate rock types (low- and high-TiO2 types) contain phenocrysts and/or microphe- nocrysts of augite (Wo3s a~), plagioclase (An67 4o), pigeonite (WOll_8) and Ti-magnetite. The groundmass is composed of plagioclase, augite, pigeonite, Ti-magnetite, ilmenite and quartz.

107

T A B L E II

Major- (wt.%), trace- (ppm) element and Sr-Nd isotope composition of low-TiO2 ( < 2 wt.% ) basalts from the southern Paran~ basin

1/44 2/46 3/46 4/47 6/48 6/49 7/50 8/61 9/52 10/53

BU652 6339 BRASCA 6BIt'TC 6U650 8U651 8U662 8302 5328 8U649

SlO 2 51 .10 51 .15 52 .66 51 .53 51 .61 52 .21 52 .08 53 .24 52 .21 52 .32

TIO 2 0,83 1,07 1.02 1.01 1,08 1,05 1,16 1.16 1.24 1.24

A1203 {5.81 15,49 14,78 16,74 15,85 15.54 15.54 ]5,88 15.51 16.08

FeO t 9,64 10.33 9,88 9.68 I0,33 10.38 10,30 10.66 11.42 10.85

MnO 0.23 0,15 0.17 0.15 0.19 0.18 0.]8 0,16 0.17 0.18

MgO 8.83 8,04 7.14 6.76 6,79 6.57 6.29 5.47 5,76 5.21

Ca~ 11,24 10.82 11.10 10,58 11,38 11.07 10.83 9,59 9,79 i0,92

Na20 1 .57 1 ,86 2 ,26 2 .32 2 ,03 2 .05 2 ,53 2 .49 2 .44 2 .13

K20 0 .55 0 ,89 0 .80 1 .07 0 .61 0 .84 0 .93 1 .16 1 .24 0 .91

P205 0.10 0,19 0.19 0.16 0.13 0.11 0.16 0.20 0,22 0.16

L .O. I . 1.43 1.31 0.90 1.71 1.03 0.92 1.33 1,22 1.30 0.82

mg * 0 . 649 0 .606 0 .594 0 .578 0 .565 0 ,557 0 .547 0 .503 0 .498 0 .488

Q * * 0 . 76 0 .52 2 .10 -~ 2 .00 2 ,53 0 .66 3 .48 1 .56 3 .80

01/6y *" . . . . . . 0.01 . . . . . . . . . . . .

Cr 497 483 186 320 198 191 107 74 62 170

NI 209 ~74 81 97 ]]1 II0 80 53 65 107

8l 219 277 306 343 202 211 278 377 401 349

Rb 16 27 23 25 13 29 29 30 29 21

Sr 196 225 207 2a0 190 188 218 238 242 208

La 14 10 11 19 13 9 ]7 23 28 18

Cs I 5 42 39 48 27 98 34 54 61 35

Zr 72 112 81 I]9 91 89 108 130 157 117

Y 17 21 20 20 19 22 26 26 30 24

{678r/66Sr) 0.70923(2) 0.70959(2) 0.70821(2) 0.70926{3) 0,70575(2) 0.70690(3) 0.70816(2) 0.71055(2) 0.71052(I) 0.71060(3) o

(143Nd/144Nd)m 0.51251(3) 0.51241(3) 0.51240(3) . . . . . . . . . . . . . . . . . . . . 0.51221{4) ....

11/54 12/55 13/56 14/57 15158 16/59 17/60 18/61 19/62

8U636 8359 5676 8288 BPCSO BPC51 BPC46 BPC54 BPC66

5102 51 ,60 52 .63 53 ,67 53 .6 ] 52 .09 53 .05 52 .83 52 ,35 52 .66

TiO 2 1,30 ].26 ].27 1.44 1.89 1,87 ],92 2.01 2.06

A1209 17.0] 16.33 15.19 15.22 ]6.63 16,22 16,32 ]6,77 16.39

FoO t 11.18 11.12 12.00 12.09 10,93 10.61 10,87 10,92 11.17

MnO 0,20 0.18 0.22 0,]9 0.]7 0,]6 0,17 0.16 0.16

MgO 5 .07 5 .04 4 .57 4 . 2 0 4 .85 4 .56 4 .54 4 .28 4 .14

C&O 10.94 9.26 9,97 9,60 8.76 8.97 8.78 8.84 5.79

Na20 1.87 2.d3 2.]6 2.65 2.93 2,85 2.86 2.94 2,94

K20 0.68 1,31 0,79 0.79 1.46 1.41 1.42 1,43 1.37

P205 0,14 0.24 0.16 0.21 0.29 0,30 0.29 0.30 O.30

L.O.I. l,aO 1.82 2.39 ].94 1,93 ],82 1.91 1,51 1.60

mg " 0 , 472 0 ,47 ] 0 . 426 0 .404 0 .473 0 .465 0 .458 0 .442 0 .428

Q ** 4.48 3,40 7.09 5,79 1.09 3.26 2,98 2.19 3.07

Ol/Hy *" . . . . . . . . . . . . . . . . . .

Cr 135 58 43 59 ) 03 87 ] 02 89 87

N I 102 54 65 46 96 84 74 95 85

5a 279 464 275 370 406 427 423 499 441

nb 26 34 2O 22 34 34 37 35 36

S r 186 235 236 220 322 326 325 336 324

La 19 25 10 22 28 29 90 33 37

Ce 47 53 40 54 68 67 68 66 68

Z r 131 161 ] 08 ] 48 186 182 186 195 ] 90

Y 29 3] 20 30 30 30 25 37 39

( 875 r / 86S r )o 0 .71203 (2 ) 0 , 71086 (2 ) 0 . 71065 (3 ) 0 , 70890 (4 ) 0 . 70726 (4 ) 0 . 70720 (2 ) 0 . 70722 (2 ) 0 , 70723 (3 ) 0 , 70721 (2 )

. . . . . . . . . . . . . . . . . . . . 0 , 51247 (3 ) 0 . 5 ] 246 (5 ) . . . . {:43Nd/14:Nd ) 0 . 51235 {3 )

CIPW normative quartz (Q), olivine (Ol), hyperstene (Hy) and atomic M g / ( M g + F e 2+ ) (rag) values calculated assuming Fe2(~JFeO =0.15; O1/Hy = olivine/hyperstene ratio. Major-element contents normalized to 100 wt.% on a volatile-free basis. (SVSr/SSSr)0 ratio computed back to 120 Ma; decay constant 787Rb = 1.42.10-11 a - 1; ( 143Nd / 144Nd) m = measured value. L.O.I. = loss on ignition (largely H20 ). Other 143Nd/ 144Nd measured ratios: B538 = 0.51241 (2); B816 = 0.51248 (3) and B1005 = 0.51247 (2) corresponding to low-TiO2 basalts from northern Paranfi (chemical and Sr-isotope data in Petrini et al., 1987).

F=

O0

TA

BL

E I

II

Maj

or-

(wt.

%),

tra

ce-

(ppm

) el

emen

t and

Sr-

Nd

iso

tope

com

posi

tion

of

hig

h-T

i02

( > 2

wt.%

) ba

salt

s fr

om t

he n

orth

ern

(37/

80 to

59/

102)

and

sout

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(60

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to

6711

10) P

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sin

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3~./B

1 39

182

40/8

3 41

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43/8

6 a.

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4518

9 47

190

48191

49/9

2 50

/93

51/9

4 52

/95

B167

BI06

BI04

B78

B24

~

B69

B78

B83

BSO

B3129

B3055

B567

B435

B3009

B832

8i02

50.48

51114

50159

52.12

80.79

50.34

49.48

51,15

51.27

5].35

49.50

50.03

5].]0

50190

50.42

50.39

T]O 2

2.24

2.46

2.4]

2.93

2.97

3.49

3.67

3.5]

3.30

3.65

2.]9

2.29

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2.35

2.29

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8

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1

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6

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4

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8

15

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FeO

t 1

2.7

9

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5

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8

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8

14

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1

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3

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1

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4

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8

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6

13

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.28

MnO

0.17

0.20

0.18

0.17

0.19

0.19

0.21

0,20

0.19

0,21

0.2]

0.24

0.22

0.20

0.20

0.20

MgO

5.12

4.77

4.62

4,22

4.51

5.13

5.03

4.40

4.22

4,38

5152

5-4~

5-28

5101

8"90

d'85

CaO

9.96

9.40

9.67

9,47

9.26

9.38

9.39

9.05

9.]0

8.62

0.46

10.]3

9.60

9.7]

9,99

]0.06

Na20

2,62

2.59

2, 7]

2.95

2.79

2.78

2,43

2.80

2.96

2.45

2.62

2.57

2.44

2,67

2.56

2,52

K20

1

.08

].

25

1

,19

].

OO

0

.89

0

.76

].

45

1

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1

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86

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00

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0.39

0.50

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0.47

0.30

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0.49

O. 44

O. 54

0.43

0.28

O. 33

0.28

O. 37

0.39

0.37

L.O.I.

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1.18

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1.46

1.62

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1.16

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0.99

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mg "

0.447

0.4

28

0

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7

0.4

12

0

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4

0.4

36

0

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0

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98

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31

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7

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25

Q

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01

93

0

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1

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..

..

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36

o. 04

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..

.

Cr

140

lO0

]O0

89

84

69

67

72

74

28

148

173

83

]18

158

122

Ni

75

55

84

74

55

62

62

85

56

28

85

82

65

68

7]

67

Ba

458

511

497

684

504

569

702

608

623

632

352

433

473

485

a21

390

Rb

24

26

23

25

26

19

33

27

22

27

2]

23

29

28

24

]5

5r

361

339

357

4761

377

503

452

44]

497

472

352

345

.336

382

344

348

La

23

30

24

:32

29

32

33

30

33

52

29

19

20

99

23

28

Ce

57

67

60

69

60

75

80

73

86

86

88

48

52

47

59

84

Zr

160

]73

160

208

283

233

240

223

233

275

154

162

]57

165

168

16l

y 28

33

3]

27

27

29

32

27

26

3]

25

30

27

33

30

33

( 875r/86Sr )

0.70623( 21

0.70596(2)

0.70606(2)

0.70576( ] )

0.70555(2)

0,7058] (21

0.70572(2)

0.70577[ 1 )

0.70580(2)

0.70592(2)

0,70599(2)

0.70573(2)

0.70587(2)

O. 70584(2 )

(]./058] (2

) 0.70578(21

o ( ]

AS

Nd

/14

4N

d)

0.5

]24

2

(4)

0.5

12

35

(41

0

,5]

24

4(2

) 0

.51

24

4(2

) 0

.51

24

3{2

) 0

.61

24

6

(2)

0,5

12

38

(21

0

,51

24

3(2

) 0

,51

24

2(1

1

0.5

12

44

(2)

....

0

.51

24

4(1

)

0,5

12

46

(1)

0,5

12

43

(3)

..

..

..

.

TA

BL

E I

II (

cont

inue

d)

53/9

6 54

/97

88/9

8 56

/89

57/1

00

58/1

01

59/1

02

60/1

03

61/1

04

62/1

05

63/1

06

64/1

07

65/1

00

66/1

09

67/1

10

6420

B

3022

64

06

63C

~7

I~1

B

~

8~

31

66

6254

B

G62

56

BG

B25

7 I~

6259

80

6260

B

1~7

BR

A7C

B

RA

gCB

8i0

2

50

.65

5

0.3

0

50

.40

5

2.0

7

52

.37

5

0.9

6

51

.53

5

1.7

0

52

,21

5

2.6

2

50

.44

5

2.8

6

50

.47

5

0.4

1

5].

65

TiO

2

3.0

1

2.7

7

3.0

3

3.2

4

3,7

6

3.3

6

3.6

6

2.0

2

3.4

1

3.3

9

3.7

6

3.4

8

4.2

8

3.8

5

2.1

8

A1

20

3

14

.46

]3

,93

]4

.]9

1

4,0

9

13

.76

1

3.5

5

]2.8

6

]4.3

0

14

.24

1

4.]

9

13

.89

1

3.7

4

14

.00

1

4.6

6

15

.47

FeO

t ]3

.29

1

3.6

3

13

.43

]2

.57

1

2,1

5

14

.28

]4

.22

1

4.2

2

11

.6]

1].

26

1

21

82

]2

10

2

12

.77

1

21

95

1

].5

2

MnO

0

,20

0

.22

O

.20

0

.17

0

.16

0

.20

0

.22

0

.22

0

.11

0

.11

0

.]6

0

.]4

0

,]

7 0

-]5

0

.]9

MgO

4

.82

4

.92

4

.70

4

.h9

4

.37

4

.24

4

.14

4

.24

4

.52

4

.79

4

.84

4

.27

4

.80

4

.25

5

,}9

CaO

9.55

9.90

9.75

8.39

7.64

8,59

8.27

9.49

8.35

8.58

9.34

8.59

9,64

9.58

9.5]

Na

O

2.6

5

2.7

0

2.7

1

2.8

9

3.0

6

2.7

3

2.8

3

2.8

4

2.7

3

2.5

7

2.3

5

2.4

9

2.2

5

2.1

9

2.6

5

2 K20

0,94

1.18

1.14

].48

2,11

].61

1.63

0.72

2.27

1.89

1.74

1.85

1.15

1.27

],09

P2

05

0

.43

0

.45

0

,45

0

,5]

0.6

2

0.4

8

0,6

4

0,2

5

0.5

5

0,6

3

0,6

6

0.5

6

0.6

7

0.6

9

0.3

%

L.O

.I.

1.8

0

1.5

0

1.5

1

1.l

] 1

.33

].

71

1

,62

1

.87

1

.53

1

.59

2

.30

1

.84

3

.45

2

.99

2

.29

mg

* 0

.42

3

0.4

22

0

.4]4

0

.42

5

0.4

2]

0.3

75

0

.37

] 0

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8

0.4

33

0

.48

2

0.4

24

0

.4]]

0

.41

1

0,3

99

0

.46

9

Q

* 2

.55

0

.58

].

44

3

.69

3

.31

2

.42

3

.82

2

.63

2

.92

5

.08

2

.90

6

.25

5

.70

5

.34

2

.54

Ol/Hy

**

..

..

..

..

..

..

..

..

..

..

..

..

..

..

Cr

95

1

45

]0

] 3

4

50

5

0

32

52

6

6

64

5

3

72

6

8

59

74

Ni

64

6

) 5

8

34

54

4

4

33

3

4

53

52

5

9

56

58

57

56

Ba

45

5

45

] 4

66

5

40

8

15

5

30

61

1 3

64

6

64

6

2]

66

4

68

5

74

9

79

6

41

6

Rb

]6

29

2

0

27

3

7

32

38

3

5

56

5

0

38

4

5

9]

10

0

46

SF

4

52

36

1 4"

17

50

4

74

4

471

41

2

28

8

61

9

63

5

69

0

8"76

81

1 83

1 3

70

La

2

9

27

4

] 3

8

57

3

3

5]

19

44

4

5

48

4

6

57

6

2

32

Ce

79

7

4

73

7

9

ll8

9

] 9

8

58

9

5

96

9

9

88

]]

8

12

6

65

Zr

28

2

]9]

221

26

7

34

3

27

] 2

8]

16

0

3]9

3

09

3

26

2

82

3

36

3

59

2

18

Y

30

3

4

29

3

8

33

3

6

40

3

5

3]

32

3

4

3]

37

4

] 34

(87

8r/

86

8r)

0

.70

65

2(2

] 0

.70

56

8(2

1

0.'

10

56

2(2

1

0.?

05

78

(21

0

,70

50

9(1

1

0.7

05

72

(2)

0,7

05

50

(2)

0.7

07

93

(2)

0.7

08

59

(])

0,7

05

57

(2)

0,7

05

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1

0,7

05

16

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0

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47

7(2

1

0.7

04

68

(1}

0.7

07

40

(11

o

(14

3N

d/]

44

Nd

) ..

..

0.5

12

45

(11

..

..

0.5

12

46

{])

0.5

12

44

(11

0

.51

25

0(3

) .

..

..

..

..

..

..

..

..

..

..

..

..

..

..

.

CIP

W n

orm

ativ

e qu

artz

(Q

), o

livi

ne (

O1)

, hy

pers

tene

(H

y)

and

atom

ic M

g/(M

g+F

e ~+

) (m

g) v

alue

s ca

lcul

ated

ass

umin

g F

e,2O

ffFeO

=O.1

5;

O1/

Hy-

--ol

ivin

e/hy

pers

tene

ra

tio.

Maj

or-e

lem

ent

cont

ents

nor

mal

ized

to

100

wt.

% o

n a

vola

tile

-fre

e ba

sis.

(ST

Sr/S

~Sr)

o ra

tio

com

pute

d ba

ck t

o 12

0 M

a; d

ecay

con

stan

t 2S

TR

b =

1.42

-10-

"

a- 1

; ( 1

4:~N

d / 1

44N

d ) m

= m

easu

red

valu

e. L

.O.I

. = l

oss

on i

gnit

ion

(lar

gely

H~O

).

110

TABLE IV

Major- (wt. % ), trace- (ppm) element and Sr-Nd isotope composition oftholeiitic intermediate rock types from the southern (20/63 to 35/78) and northern (36/79) Paran~i basin

20163 21164 22 /55 23 /66 24z57 25 /58 26 /88 2 7 / 7 0 88171

8338 8332 8337 5364 8U659 8330 8306 8PC4 B700

s i o 2 57 .79 57 ,03 67 .33 61 .02 57 .25 56 .95 57 ,82 56 .64 59 .21

TiO 2 1.22 ],24 1.40 1.43 1,56 1.89 1.51 1.68 1.69

A1203 14199 15 .46 ] 4 . 86 14 .01 14140 ] 3 . 67 13 .80 14 .38 13 .33

FeO t 8.95 9,42 9.61 9.57 11.53 12.62 12.00 12,08 11,84

MnO 0,13 0.]3 0,14 0.13 0,19 0.]9 0.17 0,19 0.18

MgO 4.27 4,29 3.56 2,29 2.70 2.70 2.55 2.58 2.50

CaO 7.30 7.52 6.65 5,42 7.18 6.83 6,93 6.83 5.70

Na20 2 .69 2 .48 3 ,55 2 ,91 2 .85 2 .53 2 ,75 3 .27 2 ,50

K20 2 .33 2 . ] 2 2 ,61 2 .92 2 .09 2 .39 2 .25 1 .82 2 .80

P205 0 .31 0 .31 0 .29 0 .30 0 .26 0 .23 0 .22 0 .35 0 ,26

L,O.I, 1.80 1,69 1.75 1.17 0.96 1.17 1.06 1.42 2.37

mg * 0.454 0.472 0.421 0,321 0.317 0.297 0,296 0.296 0.292

Q ** 9.47 9,55 5.43 15,02 I0,]2 ]0,69 11.12 8,95 13.92

Cr 49 52 4] 29 21 31 24 22 42

Hi 32 35 28 22 28 18 19 23 17

BI 563 534 562 579 426 486 473 424 672

Rb 88 81 94 125 87 98 94 63 153

Sr 248 255 229 170 189 173 170 196 ]75

5a 43 32 35 41 25 34 29 25 136

Ce 77 76 86 79 63 72 59 62 96

Zr 297 ]44 252 260 ]75 195 2]0 164 111

Y 32 30 32 41 39 32 41 33 111

(87Sr/868C)o 0.71195(]) 0.71159(I) 0.71178(I) 0.71556(1] 0.71267(I) 0.71295(I) 0.71223{1) 0.70969(1) 0.71331(I)

(143Nd/144Nd)m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29 /72 30 /73 31 /74 3 2 / 7 5 33 /76 34 /77 35 /78 36 /79

5721 8BN2EA 8U558 58556 5851 5485 8441 B457

S102 59 .23 59 ,49 59 .49 60 . ] 8 57 .98 56 .92 56 .81 59 .17

TiO 2 1.75 1,76 1.79 1.61 1.07 1.51 1.60 1,88

81202 13 .36 12 .64 13 .05 12 ,92 14 ,50 14 .08 13 ,51 12 .82

FeO t 12 .06 12 .21 12 .14 12 .01 ] 0 . 12 11 .76 12 .73 11 .87

M.nO 0.]7 0,17 0.17 0,16 0,18 0,19 0,17 0.2]

MgO 2 ,30 2 .12 2 .04 ] . 73 3 ,63 3 .21 2 ,89 1 .53

CaO 5,74 6.21 5.95 5.62 7.75 6.93 6,99 5.46

Na20 2 ,42 2 .63 2 ,53 2 ,85 2 .52 2 .94 3 ,25 3 ,24

K20 2 .71 2 .50 2 .58 2 .48 2 .08 2 .23 ] . 72 2 .95

P205 0 .27 0 .24 0 .26 0 .23 0 .36 0 .21 0 .32 0 .88

L.O.I, 1.99 2.10 ],21 1,67 1.34 0.96 1.09 ].83

m 8 " 0 , 271 0 .254 0 .249 0 .221 0 .4 ]4 0 .356 0 .309 0 .201

O ** ]4.77 14.72 15.22 15.65 10.88 8.33 8.68 ]2.79

Cr 24 25 18 19 25 31 34 8

Ni 20 7 ] 5 13 66 32 26 3

Ba 608 470 560 549 343 397 386 910

R6 109 96 I]0 306 91 88 78 86

Sr 182 203 183 ] 88 142 179 ] 64 406

La 42 34 32 44 26 29 3] 84

Ce 84 70 80 82 52 57 63 163

Zr 2;7 197 212 214 ]5] 166 173 596

Y 36 33 43 5] 32 36 37 66

(87Sr/86Sc) 0 .71391 (1 ) 0 , 7O965 ( } ) 0 , 71540 ( ] ) 0 . 71289 (1 ) 0 . 71108 (1 ) 0 . 70968 ($ ) 0 , 71317 ( ] ) 0 . 70610 ( ] ) 143 144 o

( Nd/ Nd) m

C I P W normative quartz (Q) and atomic Mg/(Mg+Fe 2+ ) (mg) values calculated assuming Fe2OffFeO=0.15. Major-ele- 87 86 ment contents normalized to 100 wt.% on a volatile-free basis. ( Sr/ Sr)o ratio computed back to 120 Ma; decay constant

143 144 ~STRb= 1 . 4 2 . 1 0 -11 a-1; ( ' Nd/ Nd)m=measuredvalue. L.O.I.=loss on ignition (largely H20).

111

TABLE V

j l s 0 - and corresponding Sr-Nd isotope compositions for low- and high-Ti02 (LTi and HTi, respectively) basalts from southern (SPP) and northern (NPP) Paran~i provinces

~ l S O ( a / " " ) 6S O L . O . I . S e c t o r S U i t e

8PP LT i 8 6 0 3 ( 1 ) a + 9 . 4 0 . 7 0 9 1 1 - - - 1 . 9 3

B 3 4 6 ( 3 ) a + 8 . 9 0 . 7 1 0 7 2 0 . 5 1 2 2 7 1 . 2 4

B R S 4 4 ( 7 ) a + 7 . 0 0 . 7 0 7 5 8 - - - 1 . 0 4

B U 6 5 2 ( 1 / 4 4 ) b + 8 . 0 0 . 7 0 9 2 3 0.5~!~251 1 . 4 3

B U 6 4 9 ( l O / 5 3 ) b + 7 .3 0 . 7 1 0 6 0 - - - 0 . 8 2

B P C 5 0 ( 1 5 / 5 8 ) b + 9 . 5 0 . 7 0 7 2 6 - - - 1 . 9 3

8 P C 5 1 ( 1 6 / 5 9 ) b + 9 . 7 0 . 7 0 ? 2 0 - - - 1 . 8 2

8PC54(18/61)b +10.5 0.70723 0.51245 1.51

8448(I0)a + 8.5 0.70463 0.51274 0.97

B3064(Ii)a + 8.4 0.70493 0.51278 1.26

8208(12)a + 7.7 0.70580 0.51264 0.95

8490(13)a + 8.2 0.70657 0.51241 1.44

8505(14)a + 8.2 0.70662 --- 1.31

8 4 4 4 ( 1 5 ) a + 9 . 2 0 . 7 0 8 7 2 0 . 5 1 2 4 8 0 . 8 8

B 2 0 4 ( 1 8 ) a + 9 . 7 0 . 7 0 8 0 8 0 . 5 1 2 4 3 1 . 1 7

8512(20)a + 8.1 0.70560 --- 1.44

B509(21)a + 7.9 0.70553 --- 1.37

8412(26)a + 8.1 0.70582 --- 1.43

BGB28ab;b + 9.8 0.70517 0.51244 2.41

B538(25)a + 9.0 0.70591 0.51241 1.78

B983(32)a + 6.7 0.70583 --- 1.74

8988(33)a + 8.2 0.70587 0.51242 1.99

B980(34)a + 7.4 0.70587 0.51242 1.91

B987(35)a + 6.9 0.70596 0.51247 b 1.52

BI007(38)a + 8.1 0.70590 --- 1.70

8979(39)a + 8.8 0.70571 --- 1.60

B187(40)a + 8.6 0.70592 --- 1.68

B192(41)a + 6.9 0.70586 --- 0.92

8194(42)a + 8.1 0.70550 0.51247 b 1.03

Bi06(38/81)b + 6.9 0.70623 --- 1.18

B72(40/83)b +i0.0 0.70578 0.51244 1.44

B80(46/89)b + 8.9 0.70595 0.512A4 1.46

B3055(48/91)b ÷ 8.3 0.70573 0.51244 1.30

B3009(51/94)b + 7.5 0.70581 --- 0.99

B232(52/95)b + 7.3 0.70578 --- 1.39

NPP

HTi

LTi

HTi

LO.I .=loss on ignition, a=Pet r in i et al. (1987) and b = present study.

4. Analytical procedures

Major/trace-element and Sr -Nd isotope compositions were determined following the

procedures described in Bellieni et al. (1983) and Petrini et al. (1987), respectively. NBS-987 Sr standard analyses gave average values of 0.71027(3) and 0.71027(2) at Pisa and Napoli laboratories, respectively; the average 143Nd/ 144Nd ratio obtained for BCR-I is 0.51271(2) (Pisa) and 0.51264 (Napoli). The Pisa data are normalized to the BCR-I value of 0.51264. Standard deviations of the isotopic ratios are expressed as 2aof the mean value. Sr blank values are < 2 ng at both laboratories.

Basalt samples for JlsO measurements were reacted for 14 hr. at 650°C with BrF5 in nickel reaction vessels. The evolved O~ was quantita- tively converted to C02 by reaction with spec- trographic graphite inductively heated in pres- ence of a Pt catalyst. The range of the oxygen yields varied by a few percent units; the standard reproducibility of the isotopic measurements was, on average, +0.2%~ ( lo) .

5. Isotope and chemical data

The new Sr-Nd isotope and chemical data essentially refer to high-TiOe basalts (Tables II-V). Average values and compositional ranges for HTiB and LTiB, including tholeiitic andesites for SPP, are reported in Table VI (Fodor et al., 1985; Mantovani et al., 1985a; Petrini et al., 1987; present study).

5. I. Isotopes

Low-TiO2 basalts from NPP have initial (120 Ma) STSr/S6Sr ratios falling within a narrow range (0.7055-0.7060), while those from SPP show a large Ro variability (0.7046-0.7120) (Fig. 2). 143Nd/144Nd ratios measured on low- TiO2 basalts from NPP vary between 0.5124 and 0.5125, while those from SPP range from 0.5122 to 0.5128. Finally, low-TiO2 basalts from NPP have 61SO-values in the range +6.7 to +9.0%~, while those from SPP vary between + 7.0 and + 10.5%~.

High-TiO2 basalts gave isotope values falling

112

T A B L E VI

Average major- (wt.%) and trace- (ppm) element composit ions of low- ( < 2 wt.% ) and high-Ti02 ( > 2 wt.% ) basalts, and low-Ti02 tholeiit ic andesites ( S P P 3 ) investigated in the present study

SPP1 ( 8 i 0 2 & 52 w t , %) SPP2 ( S i O 2 = 5 2 - 5 5 w t . %) SPP3 ( S i O 2 = 5 5 - 6 3 w t . %) SPP4 (T iO 2 ) 2 y r . %)

a v e r . r s ~ g e N s v e r , r a n g e N a v e r . r a n g e N a v e r . r s n l e N

SiO 2

TiO 2

AI203

FeO t

MDO

MgO

CsO

Ns20

K20

P205

mg

Cr

Ni

Ba

Rb

Sr

LI

Ce

Zr

Y

5 0 . 5 9 4 9 , 2 7 - 5 1 . 9 4 2 6 5 3 . 1 1 5 2 . 0 5 - 5 4 . 8 4 4 ] 5 7 . 5 6 5 5 . 2 6 - 6 1 , 0 2 2 7 5 2 . 0 8 5 0 . 4 1 - 5 5 . 7 4 1 6

1 . 3 6 0 . 8 3 - 1 . 8 9 2 6 1 . 4 6 0 . 7 9 - 2 . 0 0 41 1 , 5 3 1 . 2 2 - ] . 8 9 27 3 . 5 0 2 ,02 - 4 , 2 8 1 6

1 5 . 5 9 1 4 . 2 6 - 1 7 , 0 1 2 6 1 5 . 3 1 1 4 . 0 6 - 1 6 . 7 7 41 1 4 . 0 9 1 2 . 9 2 - 1 5 . 4 6 2 7 1 4 . 0 8 1 3 , 2 1 - 1 5 . 4 7 1 6

~],92 9,30 - 13,48 26 11.51 8.26 - 13.51 41 11.16 8,95 - 13.72 27 12.14 I0,55 - 14.22 16

0,21 0,15 - 0.33 26 0.19 0.15 - 0.24 4] 0.17 0,13 - 0.20 27 0.16 0,11 - 0.19 18

8 , 2 0 4 , 9 1 - 8 . 8 3 2 6 5 . ] 6 4 . 1 4 - 6 . 6 2 41 3 . 3 4 1 . 7 3 - 5 . 2 1 2 7 4 . 6 0 4 . 2 4 - 5 . 2 3 1 8

1 0 , 8 9 " 8 , 3 5 - 1 1 . 6 7 2 6 9 . 4 ] 7 . 7 ] - 1 1 . 7 9 41 7 , 0 4 5 . 4 2 - 9 . 5 3 2 7 8 . 7 0 6 . 2 9 - 9 . 6 4 1 6

2.43 1.67 - 2.93 26 2.57 ].92 - 3.0? 41 2,77 2.25 - 3.55 27 2,59 2.19 - 3,50 16

0.69 0,15 - 1.44 26 1.07 0.47 - 2.17 41 2,09 0.76 - 2,92 27 1,62 0.72 - 2,39 16

0.18 0,I0 - 0.26 26 0.21 O.lO - 0.30 41 0.25 0.16 - 0.36 27 0,53 0.25 - 0.69 16

0 , 5 1 3 0 , 4 3 5 - 0 . 6 4 9 2 6 0 . 4 7 5 0 , 3 4 0 - 0 . 6 5 6 4 ] 0 . 3 6 9 0 . 2 2 1 - 0 . 5 0 1 2 7 0 . 4 3 1 0 . 3 6 8 - 0 + 4 6 9 1 6

1 8 5 3 4 - 4 9 7 2 4

8 9 5 0 - 2 O 9 2 4

2 4 1 1 4 8 - 3 9 3 2 6

1 8 0 - 5 9 2 6

2 0 3 147 - 3 2 9 2 6

1 3 a - 26 2 6

3 5 1 5 - 4 8 2 3

105 72 - 132 24

2 8 17 - 5 0 2 4

8 7 3 2 - 3 1 6 3O 31 1 8 - 5 2 1 9 6 1 2 6 - 7 2 1 2

6 5 2 4 - 1 3 7 3 2 2 6 1 5 - 6 6 2 4 5 4 3 4 - 6 2 1 2

3 6 6 1 2 7 - 5 0 6 41 5 0 4 3 4 3 - 6 7 2 2 7 6 4 6 3 6 4 - 8 5 3 1 6

3 3 ] 2 - 7 2 41 8 2 2 2 - 1 5 3 27 4 5 1 4 - 1 0 0 16

2 4 5 1 5 2 - 3 7 5 4 1 1 9 8 1 4 7 - 2 8 0 2 7 6 7 0 2 8 8 - 8 7 6 1 6

2 2 8 - 3 7 3 8 3 3 21 - 4 4 21 4 5 1 9 - 6 2 1 6

5 2 1 8 -- 6 8 3 5 7 0 5 2 - 8 4 21 9 5 5 8 - 1 2 5 1 8

1 4 3 7 2 - 1 9 5 3 2 1 9 3 1 4 4 - 2 6 0 2 2 2 9 2 160 - 3 8 9 12

2 9 1 6 - 4 0 3 3 3 6 3 0 - 51 2 3 3 4 2 6 - 4 1 1 2

(878r/B6Sr)o 0,70737 0.70463-0.71203 26 0.70910 0,70720-0.71337 41 0.7123] 0.70955-0.71556 27 0.70544 0.70477-0.70650 8

(143Nd/]44Nd) 0.51249 0,51222-0.51278 ]2 0,51234 0.51219-0.51243 ]6 0.51218 --- I 0.51239 0.51239-0.51245 6 m

SlO 2

TiO 2

AI203

FeO t

MnO

MgO

CsO

NI20

K20

P205

mg

Cr

Ni

Ba

Rb

5 r

La

Ce

Z r

Y

NPPI (SiO 2 • 52 wt. %) NPP2 (TiO 2 > 2 wt. %) NPP3 (SiO 2 > 55 wt. %)

aver. range N aver. rsnRe N aver. range N

5 l , ] 1 5 0 . 2 7 - 5 2 . 1 6 1 9 5 1 . 0 9 5 0 . 3 9 - 5 4 , 6 8 2 7 5 8 . 9 8 5 7 . 2 6 - 5 9 , ] 7 2

1 . 8 1 1 . 5 1 - 2 . 0 5 1 9 2 . 8 6 2 . 1 2 - 3 . 7 6 2 7 2 , 4 2 1 . 8 8 - 2 . 9 5 2

15.19 13.44 - 17.]7 19 14,32 12,91 - 15.40 27 13,76 12.82 - ]4,84 2

12.39 11,00 - 13.71 19 ]3.06 9,86 - 14,44 27 10.9i 3C.04 - 11.87 2

0 . 2 1 0 , 1 5 - 0 . 2 4 1 9

5 . 5 0 3 . 7 0 - 6 . 4 7 ] 9

] 0 , 2 6 9 , 3 7 - 1 0 , 8 9 1 9

2 , 4 5 2 , 0 8 - 2 . 7 0 1 9

0.82 0.59 - 1.05 19

0 . 2 6 0 , 2 0 - 0 , 3 8 1 9

0 , 1 9 0 . 1 5 - 0 . 2 2 2 7 0 . 2 0 0 . ] 5 - C . 2 I 2

4 . 8 2 4 . 1 4 - 5 , 6 5 , 2 7 ] . 3 4 ] , 5 3 - 2 . 3 5 2

9 . 2 6 7 . 6 4 - 1 0 . 4 6 2 7 6 . 3 8 5 . 4 6 - 7 . ~ 9 2

2 , 7 1 2 . 4 4 - 3 . 0 5 2 7 3 . 1 4 3 , C 3 - 3 . 2 4 2

1 . 2 5 0 . 7 6 - 2 . 1 1 2 7 2 , ] 5 1 . 3 4 - 2 . 9 5 2

0 , 4 4 0 , 2 8 - 0 , 6 2 2 7 0 . 5 0 0 , 7 1 - 0 . 8 8 2

0 . 4 7 2 0 , 4 0 5 - 0 , 4 3 2 1 9 0 . 4 2 7 0 . 3 7 1 - 0 . 5 0 1 2 7 0 . 2 5 6 0 . 2 0 1 - 0 . 3 1 ] 2

104 71 - 183 19

63 45 - 104 19

345 253 - 469 ]9

16 8 - 24 19

2 8 9 2 1 2 - 3 6 9 1 9

16 8 - 2 8 1 9

41 3 2 - 6 0 1 9

119 110 - 158 ] 9

3 3 2 0 - 3 9 1 9

9 3 2 8 - ] 7 3 2 3 1 5 8 - 2 2 2

5 9 2 8 - 8 5 2 3 1 4 3 - 2 4 2

5 1 6 3 ] 9 - 8 ] 5 2 7 8 ] 3 7 1 5 - 9 ] 0 2

2 6 ] 5 - 3 8 2 7 7 0 5 4 - 8 6 2

4 3 0 2 8 4 - 7 4 4 2 7 5 0 0 4 0 6 - 5 9 4 2

3 2 1 9 - 5 7 2 7 6 9 5 4 - 8 4 2

7 0 4 2 - ] ] 8 2 7 1 3 8 1 1 3 - 1 6 3 2

2 ) 8 1 6 0 - 3 4 3 2 3 4 7 1 3 4 6 - 5 9 6 2

3 ] 2 6 - 4 0 2 3 5 2 3 8 - 6 6 2

(875r/86SF)o 0,70584 0.70550-0.70596 19 0.70572 0.70509-0.70623 27 0.70604 0+70597-0.706]0 2

( 1 4 3 N d / 1 4 4 N d ) 0 . 5 1 2 4 3 0 . 5 1 2 4 0 - 0 , 5 ] 2 4 8 9 0 . 5 1 2 4 3 0 . 5 ] 2 3 5 - 0 . 5 ] 2 5 0 ] 8 . . . . . . m

SPP = southern Paran~i basin; N P P = northern Paran~ basin. Major-element contents recalculated to 100 wt.% on a volatile- free basis. N = number of samples. (87Sr/S~Sr) o -- computed back to 120 Ma; ( 14'~Nd/144Nd),, = measured value. Sourrce isotope data: Fodor et al. (1985); Mantovani et al. (1985a); Hawkesworth et al. (1986); Petrini et al. (1987) and present study, mg = atomic M g / ( Mg + Fe 2 + ) (Fe2OffFeO = 0.15 ).

30

ZO

Si 02 (wt %)

• <52 [] 52-55 [] 55-63

JNORTHERN PARAN¢, J

Low-Ti O~t suite

.j 0704 0708 0.712 0716

Hi~lh - Ti02 suite

L

"a

0.704 0708

]0

ZO

10

ZO

10

[SOUTHERN PARANA] High - T,02 suite

Low- Ti 02 suite zo 0.704 0708 0.712 0.716 0.704, 0.708

Fig. 2. Frequency histogram of Ro (initial ~VSr/S~SSr ratio) for low- and high-TiO2 basalt-andesite suites from the southern and northern Paran~i basin. Source data: Fodor et al. ( 1985 ): Mantovani et al. ( 1985a,b ); Petrini et al. ( 1987 ); Piccirillo et al. (1987) and present study.

within a narrow range relative to low-TiQ basalts. R,)-values for high-TiO2 basalts from NPP gave 0.7051-0.7062, while those from SPP are in the range 0.7047-0.7065. The variations of 14:~Nd/144Nd for high-TiQ basalts from NPP and SPP are quite similar, 0.5123-0.5124 and 0.5122-0.5124, respectively. High-TiO.~ basalts from NPP gave 61SO-values within +6.9 and +10.0%c, while one sample from SPP gave 61sO= + 9.8Ci:c.

Intermediate rock types from SPP have high values of Ro (0.7097-0.7156) and 61sO (+11.3%~), and low ~4~Nd/144Nd ratio (0.5122). On the other hand, the rare andesitic rock types from NPP have relatively low Re (0.7060-0.7061).

113

5.2. Major and trace elements

The investigated basalts, as the majority of those from the entire Paran~i basin (Piccirillo et al., 1987 ), usually have low Mg/(Mg + Fe 2 + } ratios (mg=0.43-0.51) and therefore represent evolved magmas. Only few low-TiO.e basalts from SPP have mg in the range 0.60-0.66.

Low-TiO,e basalts from NPP are characterized by higher contents of Fe, Ti, P, Sr and Ba, and lower concentrations of Si, K, Rb, U and Th relative to those of LTiB from SPP (Table I).

It is of interest that low-TiOe basalts with mg- value > 0.60 and SiO2 < 52 wt.% have relatively high Ro values (0.7076-0.7101; av. 0.7091 ), and that the lowest values of Ro (0.7046-0.7049) are found for low-TiO,2 basalts from SPP with com- paratively low mg-values ( 0.50-0.52 ).

High-TiO,e basalts from SPP are markedly distinctive relative to NPP analogues for their higher contents of Si, K, P, Sr, Ba, Rb, La, Ce, Zr, U and Th, and lower Fe concentrations (Ta- bles I-IV and VI).

6. Fract ional crystal l izat ion and crustal contaminat ion

Mass-balance calculations (Bellieni et al., 1986b; Piccirillo et al., 1988) indicate that high- TiO.~ basalts cannot be derived from low-TiO., basalts through fractional crystallization. This implies that high- and low-TiO~ basalts reflect chemical differences in parental melt compositions. Contrarily, fractional crystallization of gabbroic assemblages (augite + pigeonite + plagioclase and minor olivine + Ti-magnetite) generally accounts for compositional variation of the low- and high-TiQ basalt (andesite) suites, respectively.

Significant positive correlations between R(~ and SiO> K20, Ba and Rb (Fig. 3 ) exist for low- TiO.~ basalt-andesite suite from SPP. This suite also shows negative correlations of Ro vs. mg- value and (Cr+Ni) (Fig. 4), suggesting that SPP basaltic melts suffered contamination with

114

L,V HTV tt 0if i ; .......... SPB - • iso

K20 • - ---- ~ol

• _ - _ _ _ J

Z • - - - - - 90

~ L A _ - _ - -

I I I 0 I I I I I h t I I A

i ,oo , . , _ 1 °° - t

,00[ --j:- --_---_ -

50 6 - -- ' " - - ZOO f

1 J i ~ I i R O I i l I i i I I I I

0.705 0.707 0209 0.711 0.713 0 715 0.705 0.707 0.709 0.711 0.713 0.715

Fig. 3. R~) (S~Sr/S~Sr initial ratio) vs. Si02 and K~O (wt.%), and Ba and Rb (ppm) for low- and high-TiO~ basalt-andesite suites (LTi V and HTi V, respectively ) from the southern ( S P B ) and no rthern ( N P B ) Paran~i basin. Source data: see caption of Fig. 2.

granitic components concurrently with fractional crystallization (e.g., AFC (assimilation- fractional crystallization); DePaolo, 1981). However, the least evolved basalts (mg > 0.50) point to a positive correlation of Ro vs. mg and (Cr + Ni) which corresponds to a negative correlation between the degree of contaminat ion and the degree of magma fractionation. This indicates that the most primitive and, therefore, hottest magmas can become more contaminated (mixing processes) than an evolved magma (Hupper t and Sparks, 1985). The role

of mixing and AFC processes in the evolution of the low-TiO2 basalt suite from SPP appears to be supported by mg vs. 14:~Nd/144Nd relationships which show distinct trends originating from basalts with different degrees of evolution (inset of Fig. 4 ).

AFC modelling for the low-TiO,~ basal t -andesite suite from SPP (Fig. 5) is, in general, consistent with an assimilation/crystall ization ratio of 0.1-0.2 for a granitic contaminant with Sr = 290 ppm and Ro -- 0.740 and parent basalts with Ro-- 0.7040 and Sr-- 150-300 ppm. It is ap-

7 0 0 - -

600

500

400

300

Z00

100

07

0.5

0.5

0z,

02

L

~ - _ - - ---_ ~k,_ - _ ~ ' ~ _ _ _ - " < - - . ~ = _ - _ _

_- - ~ -

m g _ . , g _ ;-

-__ % - 05122 0.5127

-%_-7__ _ - _ - - - 1_~:_ __---

-: :-- _ --- - _ T_

0705 0.707 0.709 0.711 0.713 0.715 Ro

Fig. 4. Ro (S:Sr/S(~Sr initial ratio) vs. mg [atomic Mg/ ( M g + F e ~ + ) , Fe._)O:JFeO=0.15] and Cr+Ni (ppm) for low-TiO_, basalt-andesite suite from the southern Paranfi basin. 14:~Nd/~44Nd ratio = measured value (inset). AFC: see text h)r explanation. Source data: see caption of Fig. 2.

parent from Fig. 5 that basalt suites from NPP do not show evidence of crustal contamination.

The 5'sO vs. Ro plot (Fig. 6) shows that northern Paran~i basalts have a large 6~sO variation ( + 6.5 to + 10.0%~, ) for a virtually constant Sr-isotope ratio. A similar 6~sO variation was also found for southern Parami basalts without apparent correlation with R0. Thus 6 ~sO variation probably results from water-magma interactions and/or post-eruptive processes. O- and H-isotope studies on mineral separates are necessary to evaluate this problem.

7. Mantle source he terogene i ty

Previous studies (Bellieni et al., 1984c; Pe- trini et al., 1987) have shown that low- and high-

115

Ro

0.715

0.71/,

0.713

0.712

0.711

0.710

0.70...

0.708

0.707

0.706

0.705

0.70~

. . . , . . . . , . , . . . . , . . . . , . . . . , . . . . , , . .

' t " t '~ F L T i V H T i V

NPB ~ • SPB •

r-

"i F- 1 Contam,na n t

, Sr : 290 ( p p m )

! Ro: 0.%0 I " ~ :AB:~01 ; 6S; 70 8 /

BC: ,, ; ,, : 1 . 2 ~

: ~ , , , , , , A 1 S l i , : o 2 ; ~ : ;o.8 E - ~ '~ B l C l : ,, ; ,, : 1 2 j

((17

(0.9)

B ( o n d e s , t e ) - - ( o n d e s i t e ) (0.7). , / . / - -

i . • ,." ,2 (0.9) • / •

( o n d e s i t e ) / A

, 1 . . . . i . . . . i , , , ,

. . . . . z;0 . . . . 3 ~ o ~.;o . . . . s;o"' 0oo 7oo S r

Fig. 5. Sr (ppm) vs. R. (~:Sr/S~Sr initial ratio). Assimila- tion fractional crystallization model for low-TiO~ basalt = andesi te suite from the southern Parand basin (SPB). In brackets the fraction of residual liquid, r = assimilation/ crystallization ratio; D=bulk partition coefficient; NPB, S P B = northern and southern Paranfi basin, respectively; LTi V, HTi V = low- and high-TiO~ volcanics.

Ti02 "uncontaminated" (Ro < 0.7060) basalts from the Parand basin are related to different primary melts. Such tholeiitic melts may be related to; (1) different degrees of melting of a homogeneous source (e.g., garnet peridotite: HTiB=5% and LTiB=20%; Piccirillo et al., 1988a), or (2) different mantle sources (i.e. similar melting degrees for HTiB and LTiB).

Sr (Ro) and Nd (present day) isotopes (Fig. 7) indicate that most of the basalts from NPP (LTiB and HTiB) plot in the mantle array (Dosso and Murthy, 1980) at low 14:~Nd/144Nd

ratios and high Ro-values (0.5124 and 0.7060, respectively). In contrast, low-TiO., basalts from SPP form a trend which progressively de- parts from the mantle array (Ro = 0.704, '4"~Nd/ 144Nd=0.5128) due to an increase of Ro and a decrease of Nd-isotope ratios. This trend also

116

,10

[

.7~ I

LTZB HT_,B NPP o •

SPP ~ •

A Zi

~' o I A s

/ OC~

IO i

I '\

07050 ' 07070

+10.- -,~

8 ~ '~ NPP ~'o

+7 " '

J I "'~

zi z~

zl

I~! Nd/~"Nd)m

0 51Z] 0 51~5 0 51Z7

A

t l

A

,'JTSr/~Sr)o 1

0.7090 07110

Fig. 6. Oxygen isotopic composition vs. Ro (~VSrff6Sr initial ratio) and low- and high-TiO~ basalts (LTiB and HTiB, respectively) from the northern (NPP) and southern (SPP) Paran~ basin. ~ s O are given vs. V-SMOW standard as defined by Gonfiantini (1978).

:\

0 5Q~

' LTV HTVI SPB ~

[NPB c . . [

- z

Ro

7[] 0 705 O 707 0 70~ D.711 0.71] 0715

A

' a

" Z,4a

zx, a '

Ro

Fig. 7. t?. (STSrff~Sr initial ratio ) vs. ( 14:~Nd/144Nd)m present-day ratio for low- and high-Ti02 basalt-andesite suites ( LTi V and HTi V, respectively ) from the southern (SPB) and northern (NPB) Parand basin. Source data: Hawkes- worth et al. ( 1984, 1986); Mantovani et al. (1985a); Petrini et al. {1987) and present study. Mantle array, KG (Ker- guelen islands) and TC (Tristan da Cunha) after Dosso and Murthy (1980); SWIR (South Western Indian Ridge ) and B (Bouvet island) after Le Roex et al. {1983); and W.R. (Walvis Ridge ) after Richardson et al. ( 1982 ).

fits the basalt-andesite suite from Etendeka (Namibia; Hawkesworth et al., 1984) which corresponds, for age and composition, to the low-TiO2 basalt-andesite suite from SPP (Pic- cirillo et al., 1987 ). Such a trend is roughly consistent with binary mixing between basalts plotting in the mantle array and granitic crustal components, and is essentially similar to that formed by Deccan basalts in India (Ambenali and Poladpur formations) which formed with contribution of crustal granitic contamination (Cox and Hawkesworth, 1984, 1985).

It is remarkable in the plot of R. vs. (1000/ Sr) (inset of Fig. 7 ) that low-TiO~ basalts from SPP merges with the trend of Walvis Ridge basalts (Namibia) towards the low-R,, end (0.7041), while high-TiO2 basalts point towards the high-R0 end (0.7051) of this trend. This supports the view that two distinct mantle sources existed tbr the Paranfi basalts: (A) Ro=0.704 and 14:~Nd/144Nd=0.5128 for SPP (LTiB); and (B) Ro=0.706 and H:~Nd/ 144Nd= 0.5124 for NPP (HTiB and LTiB ). No- teworthy is that most of the high-TiO~ basalts from SPP generally have R0-values lower than those of high-TiO2 basalts from NPP (av. 0.7052 and 0.7057, respectively), and the lowest Ro-values (0.70468-0.70485) are quite similar to those found for low-TiO2 basalts from SPP ( 0.70463-0.70496 ).

Assuming that Paran~ basalts with Ro< 0.7060 are only slightly contaminated or "uncontaminated", the isotope variations might be compatible, at least partly, with mixing processes. A simple binary mixing model of the A- and B-type basalt end-members requires that all combinations of elements and ratios form mixing arrays (Langmuir et al., 1978). The combined distribution of Ba, La, Zr and Y, and Ro vs. STRb/S6Sr (Fig. 8) rules out a mixing model restricted to two components, even tak- ing into account the variations of interelemen- tal ratios related to magmatic fractionation. These data and the high Ba content relative to Zr (inset of Fig. 8) of the Paran~ basalts with R,,< 0.7060 do not support significant contri-

117

26

2Z

cl r n

10

6

2

' ' • ' o '

. ~Jo.7o~

~ 07O5O • A /

AJ07046 • , ( TRb/ S.)4 O " "

/

L / . <f,~, ~ ~" _ _ S P B A & z/.-

z 8 1o Z r / Y

g°° I Be • .=

7oo I . . ' , '~

5oo~ . / s . , , ,

300 j ~ ~-~(E-.o~

~=~=~ ~:~ N" MORB

100 p7 - --

- , , Z r

100 200 300 40(2

Fig. 8. Zr/Y vs. Ba/Y for low- (LTiB) and high-TiO~ (HTiB) basalts with STSrff"Sr initial ratio < 0.7060 from the northern (NPB) and southern (SPB) Paran~ basin; Walvis Ridge (Erlank et al., 1984); and South Western Indian Ridge (E-MORB and N-MORB; Le Roex et al., 1983). r= linear correlation coefficient.

bution by N- and E-types mid-ocean ridge basalts (MORB) (Le Roex et al., 1983) as depleted and enriched end-members, respectively, in a two-component mixing model. Actually, chemical and isotope compositions of "uncontaminated" basalts from the Parand basin sug- gest that they may be derived by partial melting of a heterogeneous mantle with relatively low and high content of "enriched" components (LTiB and HTiB, respectively), as proposed by Richardson et al. (1982) for the Walvis Ridge basalts.

Low- and h igh-TiQ basalts from the Paran~i basin have La /Ta ratios, normalized to primordial mantle, of > 1.0. A Ta negative anomaly relative to K (Fig. 9) exists for low- and high- TiO~ basalts from SPP with Ro = 0.7049 (K/Ta: LTiB=0.76, HTiB-0.52), but not for the basalts from NPP with the lowest (0.7051-0.7055) Ro-values (K/Ta: LTiB= 1.43, H T i B = 1.31). Noteworthy is that these differences in K /Ta ratios do not appear related to the redistribu-

tion of K under low-grade chemical alteration since the considered samples have low values of loss on ignition, and are petrographically very little altered. It is therefore argued that the different mantle-normalized K /Ta ratios between SPP and NPP "uncontaminated" basalts may be related to the retention (NPP) or absence of retention (SPP) of K by a residual phase (e.g., mica, amphibole). On the other hand, the Ta negative anomaly relative to La (Fig. 9) for all the Paran~ basalts with the lowest Ro-values might be related to the retention of Ta by an accessory phase (sphene, ilmenite, rutile?: Weaver and Tarney, 1983; unknown phase (s): Thompson et al., 1983) in the residual mantle. Thus the "enriched" components in the northern Paran~i mantle might be related to small- volume melts which left K- and Ta-bearing accessory phase in the residual mantle. Notably distinct negative depletions of Nb relative to K and of Ta relative to La are also shown by Wal- vis Ridge basalts (primordial-mantle normal-

118

1o0

60

i,° ~5

\

a_ 6 E O

L

, , , . . . . . , . . . . . . . ,

LTiB HTiB

SPB ,,x

; i ,

~'~/ " 8 3054 ~ (Ro : 0 7 0 4 9 4 )

Primordial mantle (ppm) co

''T' . . . . . . . . . . . . . Rb Ba h U K Ta La Ce Sr Nd P Hf Zr SmTi Tb

Fig. 9. Low- and high-TiO2 Paran~i basalts (LTiB and HTiB, respectively) with 87Sr/8~Sr initial ratio (Ro) ~<0.70550 normalized to primordial mantle (Jagoutz et al., 1979; Wood, 1979). Note that LTiB and HTiB from southern Paranfi (SPB) do not show Ta depletion as on the contrary do the basalt analogues from northern Parand (NPB).

ized K / N b = 1.2, L a / T a = 1.4; Humphris and Thompson, 1983; Richardson et al., 1984 ) which are believed to be derived from mantle sources variously enriched in small-volume melts and metasomatic fluids (Richardson et al., 1982). However, it must be noted that Ta (Nb) depletion may also be due to contamination of the mantle sources by crustal components (e.g., subducted sediments or metasomatism of large ion lithophile (LIL) elements ultimately derived from continents; Weaver and Tarney, 1983).

8. Concluding remarks

(1) Chemical and isotope data indicate that in northern Paran~i high-TiO2 (and low-TiO2) basalts can be considered uncontaminated or slightly contaminated by crustal materials. Is- otopically these basalts are characterized by Ro = 0.7050-0.7060 and 14aNd/144Nd= 0.5124- 0.5125.

(2) The majority of low-Ti02 basalts from southern Paran~i shows evidence of crustal contamination by granitic components. Basalts which can be considered uncontaminated or slightly contaminated have Ro = 0.7046-0.7049 and 143Nd/144Nd=0.517-0.5128. The scarce high-TiQ basalts from SPP tend to have Ro- values similar to those of low-TiO~ analogues (Ro<0.7050), and 14:~Nd/'44Nd ratios more similar instead to those of HTiB from NPP (0.5124-0.5125).

(3) Important chemical and isotopic differences between the basalts from southern (LTiB) and northern (HTiB) Paran~i indicate distinct mantle sources and a large-scale heterogeneity.

(4) Tentatively, the tNd cm~ model age of 0.5-1.0 Ga calculated for the Paran~i "uncontaminated" basalts might represent the timing of the last stabilization of the large-scale mantle heterogeneity. This may be related to the Brazilian tectonic-magmatic cycle which, possibly reworked older crust (e.g., Hawkesworth et al., 1986).

(5) Chemical and isotopic similarities between the Paran~i and Karoo basalt volcanism in Brazil and southern Africa, respectively, and its distinction in low- and high-TiO2 provinces (Cox, 1988) indicate a widespread large-scale heterogeneity of the subcontinental m~ntle. In addition, the important difference in age ( > 50 Ma) between Karoo and Paran~i volcanisms suggests that in large areas of Gondwana basalt generation probably occurred in the lithospheric mantle.

Acknowledgements

The authors have greatly benefitted from the critical review and the very helpful suggestions of Dr. A. Cundari. The manuscript was consid- erably improved by Dr. A. Prinzhofer and an- other unnamed referee.

The authors wish to express their thanks to CNPq, FAPESP, FINEP (Brazilian agencies), MPI and CNR (Italian agencies) for the finan-

cial support. They wish to thank particularly G. Mezzacasa, P. Da Roit and A. Giaretta (Uni- versity of Padova ) and B. Biasioli and R. Zettin

119

(University of Trieste) for their precious col- laboration in the analytical and technical work.

A p p e n d i x - E s s e n t i a l m i n e r a l a s s e m b l a g e s

Southern Parana Province:

Sample 1/44 Sample 2/45 Sample 3/46 Sample 4/47 Sample 5/48 Sample 6/49 Sample 7/50 Sample 8/,51 Sample 9/52 Sample I0/53 Sample 11/.54 Sample I2/55 Sample 13/56 Sample 14/57 Sample 15/58 Sample I6/59 Sample 17/60 Sample I8/61 Sample I9/62 Sample 20/63 Sample 21/64 Sample 22/65 Sample 23/66 Sample 24/67 Sample 25/68 Sample 26/69 Sample 27/70 Sample 28/7I Sample 29/72 Sample 30/73 Sample 31/74 Sample 32/75 Sample 33/76 Sample 34/77 Sample 35/78 Sample 60/103 Sample 61/104 Sample 62/105 Sample 63/106 Sample 64/I07 Sample 65/108 Sample 66/109 Sample 67/110

BU652:32.595 ° S; 56.513 ° W B339:29.472 °S; 51.353 °W BRA5CA: 28.780°S; 49.890 °W BBM7C: 29.563 ° S; 50.184 ~W BU650:32.649 ° S; 56.548 ° W BU651: 32.640°S; 56.547°W BU662: 31.003°S; 56.903°W B302:29.480 ° S; 50.701 ° W B328: 29.417°S; 51.138°W BU649:32.689 ° S; 56.581 ~ W BU636:33.432 ° S; 56.452 ° W B359:29.051 °S; 51.558°W B676:30.432 °S; 56.339°W B288:29.235 ° S; 50.186 ° W BPC50:29.130 ° S; 50.080 ° W BPC51: 29.130°S; 50.080°W BPC46: 29.130°S; 50.080°W BPC54: 29.130°S; 50.080°W BPC55:29.130 ° S; 50.080 ° W B338:29.488 ~ S; 51.358 ° W B332: 29.450°S; 51.147°W B337:29.491 °S; 51.358°W B364: 29.018°S; 51.558°W BU659: 30.811°S; 56.165 °W B330: 29.426° S; 51.142~W B306:29.476 ° S; 50.682 ° W BPC4: 29.130°S; 50.080°W B700:29.480 ° S; 50.080 °W B721: 29.637° S; 53.790°W BBM2EA: 29.563 ° S; 50.184°W BU668:30.730 ~ S; 56.732 ° W BU656:31.135 ° S; 56.026°W B85I: 26.956° S; 51.823 °W B486: 26.493°S; 51.225 °W B441: 25.467° S; 51.649°W BGB254:28.336 ~ S; 49.639 °W BGB256: 28.336°S; 49.639°W BGB257: 28.336°S; 49.639°W BGB259:28.336 ° S; 49.639°W BGB260: 28.336°S; 49.639°W BRA7: 28.780°S; 49.890°W BRA7C: 28.780°S; 49.890°W BRA9CB: 28.780°S; 49.890°W

Northern Parana Province:

slightly porphyritic TB = ol, pl, cpx, (pig) and op slightly porphyritic TB = ol, cpx, pig, pl and op subaphyric TB- - cpx, pl, pig and op aphyric TB = cpx, pl, pig and op slightly porphyritic TB = ol, pl, cpx, and op slightly porphyritic TB =ol, cpx, (pig), pl and op slightly porphyritic TB =ol, cpx, (pig), pl and op subaphyric AB--cpx, pl, pig and op aphyric TB = cpx, pig, pl and op moderately porphyritic TB = (ol), cpx, pig, pl and op moderately porphyritic AB = (oi), pl, cpx, pig and op subaphyric AB = cpx, pig, pl and op subaphyric AB-- pl, cpx, pig and op subaphyric AB = (ol), cpx, pl, pig and op porphyritic AB =pl, cpx, ol and op porphyritic AB =pl, cpx, ol and op porphyritic AB =pl, cpx, ol and op porphyritic AB--pl , cpx, ol and op porphyritic AB = pl, cpx, ol and op slightly porphyritic AND -- cpx, pig, pl and op slightly porphyritic AND = cpx, pig, pl and op slightly porphyritic LAND = cpx, pig, pl and op slightly porphyritic DAC -- cpx, pig, pl and op aphyric AND = cpx, pig, pl and op aphyric AND = cpx, pig, pl and op subaphyric AND = cpx, pig, pl and op slightly porphyritic AND = cpx, pig, pl and op aphyric AND = cpx, pig, pl and op slightly porphyritic DAC -- cpx, pig, pl and op subaphyric AND = cpx, pl and op subaphyric DAC = cpx, pl, pig and op subaphyric DAC =pl, cpx, (pig) and op moderately porphyritic AND = cpx, pig, pl and op slightly porphyritic AND = cpx, pig, pl and op moderately porphyritic AND = cpx, pig, pl and op aphyric AB=cpx , pl, (ol) and op slightly porphyritic AB = cpx, pl, (pig) and op slightly porphyritic AB --pl, cpx, (pig) and op moderately porphyritic AB =pl, cpx, pig and op slightly porphyritic AB =pl, cpx, pig and op slightly porphyritic AB = pl, cpx, ol and op slightly porphyritic AB = pl, cpx, ol and op slightly porphyritic AB = pl, cpx, (ol) and op

Sample 36/79 B457:26.033 ° S; 51.722 °W slightly porphyritic LAND = cpx, pig, pl and op Sample 37/80 B167:23.273 °S; 47.936°W granular TB =ol, cpx, pig, pl and op

120

Appendix (continued)

Northern Parand Province (cont.):

Sample 38/8I Sample 39/82 Sample 40/83 Sample 41/84 Sample 42/85 Sample 43/86 Sample 44/87 Sample 45/88 Sample 46/89 Sample 47/90 Sample 48/91 Sample 49/92 Sample ,50/93 Sample 51/94 Sample 52/95 Sample 53/96 Sample 54/97 Sample 55/98 Sample 56/99 Sample 57/I00 Sample 58/I01 Sample 59/I 02

B106:22.891 °S; 47.078:W B104:22.891 °S; 47.078~W B72:20.000 c S; 47.784°W B24: 21.336°S; 47.686°W B88:19.709 ~S; 47.961 °W B69: 20.313°S; 47.802 °W B78:20.0003 S; 47.784 ~ ) B83: 19.818~S; 47.882°W B80:20.000 c S; 47.784 ~W B3129: 27.034° S; 55.215 W B3055:25.877 °S; 54.483 W B567:25.563 ° S; 51.009 ~W B435:25.399 °S; 52.438~W B3009:25.570 ~ S; 54.613 :W B232:26.441 ~ S: 52.270 °W B420:25.695: S; 52.267 °W B3022:25.386 ° S; 54.514 W B406: 25.666° S; 52.141 ~W B3007:25.450 ° S; 55.000 ~ W B481:26.382 ° S; 51.282°W B408:25.683 ° S; 52.150°W B3031: 25.386° S; 54.223 :W

granular A B = (ol), cpx, pig, pl and op granular TB = ol, cpx, pig, pl and op slightly porphyritic AB = cpx, pig, pl and op slightly porphyritic AB = cpx, pig, pl and op slightly porphyritic AB = (ol), cpx, pig, pl and op slightly porphyritic AB = (ol), cpx, pig, pl and op moderately porphyritic AB = (ol), cpx, pig, pl and op slightly porphyritic AB = (ol), cpx, pl and op subaphyric AB =pl, cpx and op slightly porphyritic TRB = (ol), cpx, pig, pl and op slightly porphyritic TB = ol, cpx, (pig), pl and op granular AB =cpx, pig, pl and op slightly porphyritic AB = ol, cpx, (pig), pl and op slightly porphyritic TB = ol, cpx, pl and op slightly porphyritic TB = ol, cpx, (pig), pl and op slightly porphyritic AB = ol, cpx, pl and op slightly porphyritic AB =ol, cpx, pl and op slightly porphyritic AB = epx, (pig), pl and op slightly porphyritic AB =ol, cpx, pig and op subaphyric AB = (ol), cpx, pl and op slightly porphyritic AB = ol, cpx, (pig), pl and op granular AB=ol , cpx, (pig), pl and op

Classification (De La Roche et al., 1980; Bellieni et al., 1981 ): TB = tholeiitic basalt; TRB = transitional basalt: AB = tholeiitic andesite-basalt; AND = tholeiitic andesite; LAND = latiandesite and DAC = dacite. Modal phenocryst ( 0.5-2 mm ) content (vol. % ): aphyric = 0; subaphyric = 0-5; slightly porphyritic = 5-10; moderately porphyritic = 10-15; porphyritic = 15-20; and strongly porphyritic > 20. Minerals: ol = olivine; cpx = augite; pig -- pigeonite; pl = plagioclase and op -- opaques. Others: Latitude ( south ) = S, longitude (west) -- W; ( ) -- minor amount.

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Documents

Regional variations within the Paraná flood basalts (southern Brazil): Evidence for subcontinental mantle heterogeneity and crustal contamination