0 5 km

B T

S F

b

c

de

Manujan

Chah Shahi

Mt. Zandan

N

27°15’27°20’

57°3

5’57

°30’

Sorkhband Unit

North Makran

Eocene - Oligocene succession

Bajgan Complex

Quaternary deposits

Durkan Complex

Carbonatic and silicicla-stic succession

UnconformityStratigraphic boundaryNormal and strike-slip faultThrust

Location of the studied transects:

Zandan (Fig. 4b)

B T:S F:

Bashakerd ThrustSabzevaran Fault

Chah-e Shahi 1 (Fig. 4d)

b

c

d

e

a

Chah-e Shahi 2 (Fig. 4e)

Manujan (Fig. 4c)

Met

a-Vo

lcan

ic

Sequ

ence

Mas

sive

Mar

ble

Met

a C

herty

-Lim

esto

nean

d Sh

ale

Volc

ano-

Sedi

men

tary

Sequ

ence

Mas

sive

Li

mes

tone

Sabz

evar

an F

ault

Volc

ano-

Sedi

men

tary

Sequ

ence

Lim

esto

nean

d Sh

ale

Volc

anic

Se

quen

ce

Lim

esto

nean

d Sh

ale

Volc

ano-

Sedi

men

tary

Sequ

ence

Volc

anic

Se

quen

ce

Met

a Vo

lcan

o-Se

dim

enta

rySe

quen

ce

Che

rty-L

imes

tone

and

Va

ricol

oure

d Sh

ale

Volc

anic

Seq

uenc

eVo

lcan

o-Se

dim

enta

rySe

quen

ce

Massive Marble

Volc

anic

Seq

uenc

eVolc

ano-

Sedi

men

tary

Sequ

ence

MetaVolcano-Sedimentary

Stratigraphic columns not to scale

coherent successionthrust zone

Zandan transect Manujan transect

Chah Shahi 1 transect Chah Shahi 2 transect

Che

rty-L

imes

tone

and

Bas

alt

Che

rty-L

imes

tone

and

Bas

alt

WSW ENE W E

SSW NENNE - SWWSW ENE

b c

d e

b1 b2

BajganComplex

c1

Eocenesuccession

c2

c3

d3

d1 d2

e1

e2

e3

e4

e5Bajgan

Complex

Massive lava and meta-basalts

Volcanoclastic arenite

Volcanic and mixedvolcanic-carbonatic breccia

Mixed carbonatic-volcanic arenites

Shale and marl

Limestone

Carbonatic breccia

Chert

Cherty-limestone

Pillow lava

Key for stratigraphic columns

Metamorphic rocks

Fig. 5a

Fig. 5b

Fig. 5c

Fig. 5d

Fig. 5e

Fig. 5f

Fig. 5g

Fig. 5h

a b c

lim

lim

vss

ml

d

basbas

e f g h 10 cm2 m

vulcaniclasticarenite

La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

1000

100

10Roc

k/C

hond

rite

1La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Roc

k/C

hond

rite

La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Roc

k/C

hond

rite

Group 1 Group 2 Group 31000

100

10

1

1000

100

10

1

MK 364MK 365MK 369MK 483MK 484

MK 493

MK 372MK 373MK 375MK 376

MK 480MK 482

MK 867MK 282MK 338MK 795

MK 491MK 494

MK 479MK 870MK 876MK 879

MK 479MK 291MK 339MK 340

MK 500MK 506

MK 499MK 497MK 859MK 894MK 907

MK 482

MK 818

B) D) F) 0.01 0.1 1 10 1000.01

0.1

1

10

100

1000

ThN

NbN

N-MORB

E-MORB

OIB

IAT & Boninite

CAB

MTB & D-MORB

no subduction components

increasingsubduction components

Continental margin volcanic arc

Forearc & intra-arc

Nascent forearc

Subduction-unrelatedoceanic setting

Group 1Group 2Group 3

0 100 200 3000

5

10

Th/T

a

Zr (ppm)

15

400 500

UCC

APS

N-MORBOIB

Iceland plume basalts

Con

tinen

tal m

argi

n ba

salts

Group 1Group 2Group 3

Cre

tace

ous

Late

Early

Valanginian

Hauterivian

Barremian

Aptian

Albian

Cenomanian

Turonian

Coniacian

Santonian

Campanian

Maastrichtian

StageSeriesSystem

139.8

132.9

129.4

125

113

100.5

93.9

89.8

86.3

83.6

72.1

Zandantransect

Chah Shahi 1and 2 transects

Manujantransect

* Foraminifera data* Radiolarian, foraminifera and calcareous nannofossils data

Mas

sive

Lim

esto

ne

Vulcano-SedimentarySequence

Che

rty-L

imes

tone

an

d Ba

salts

Che

rty-L

imes

tone

an

d Ba

salts

*

* *

*

The Durkan Complex in the western Makran Accretionary Prism (SE Iran): Evidence for a Late Cretaceous tectonically disrupted oceanic seamount

Barbero, E.1 (edoardo.barbero@unife.it), Delavari, M.2, Dolati, A.2, Pandolfi, L.3-4,

Marroni, M.3-4, Saccani, E.1, Chiari, M.5, Luciani, V.1, Catanzariti, R.4

Dipartimento di Fisica e Scienze della Terra, Università di Ferrara1

Dipartimento di Scienze della Terra, Università di Pisa3Faculty of Earth Sciences, Kharazmi University, Tehran, Iran2

Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Pisa4

Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Firenze5

EGU 2020 Sharing Geoscience Online © Authors. All rights reserved

Bandar Abbas

Muscat

Karachi

Jiroft

Khash

Saravan

Nikshahr

Chabahar

Bandar-e-Jask

Oman Sea

Mashkel Depression

Iranshahr

Kahunj

Inner Makran

Outer Makran

Coastal Makran

Off-shore Makran

Jaz M

urian depression

Lut block

Sistan Suture Zone

Afghan block

M S

N F

C-O

F

28°N

26°N

100 km24°N

66°E64°E62°E60°E58°E

N

Makran

North

C-OFMSNF

-Chaman- Ornach Nal fault system-Minab-Sabzevaran-Nayband fault

BTGGT

CKT

Fig 2c

BTGGTCKT

-Bashakerd Thrust-Ghasr Ghand Thrust-Chan Khan Thrust

Manujan

Dar Anar

Remeshk

Fannuj

Maskutan

Qualeh Ganj

Kahnuj

B T

G G TC K T

J A Z M U R I A N D E P R E S S I O NB T D A F

57° 30’ E

27° 3

0’ N

58° 00’ E 58° 30’ E 59° 00’ E 59° 30’ E 60° 00’ E

27° 0

0’ N

26° 3

0’ N N

20 km

ZAGROS FOLD AND THRUST BELT

Quaternary deposits

Middle Miocene - Plioce-ne shallow marine and continental succession

Coastal Makran domainMAKRAN ACCRETIONARY PRISM

Outer Makran domain

Inner Makran domain

Late Miocene - Pliocene shallow marine successions

Early - middle Miocene flysch and shallow marine successions

Eocene - Oligocene flysch successions

North Makran domain

Nor

ther

n op

hiol

ites

Eocene - Oligocene episutural successionsGanj Complex

Band-e-Zeyarat

Remeshk-Mokhtarabad

Fannuj-Maskutan

Deyader Complex

Durkan ComplexBajgan Complex

Coloured Mélange

Thrust and reverse faultNormal and strike-slip fault

BTDAFGGTCKT

- Bashakerd Thrust- Dar Anar Fault- Ghasr Ghand Thrust- Chan Khan Thrust

Sorkh Band and Rudan ultramaficrocks

Fig 3a

The Makran Accretionary Prism has been subdivided in four fault-bounded tectono-stratigraphic do-mains, that are, from North to South: i) North Makran ii) Inner Makran iii) Outer Makran and iv) Coastal Makran (Figs.1, 2). The Inner, Outer and Coastal Makran are characterized mainly by Eocene to Plioce-ne deep to shallow water sedimentary succession (Burg, 2018), whereas the North Makran consists of an imbricated stack of south-verging metamorphic and non-metamorphic continental and oceanic units (e.g., McCall & Kidd, 1982; Burg, 2018). The North Makran domain record the pre-Eocene geodynamic history of the Makran Accretionary Prism (McCall & Kidd, 1982;Burg, 2018; Saccani et al., 2018; Barbe-ro et al., 2020).The Durkan Complex is one of the major tectonic elements of the North Makran and consists of several tectonic slices, which include deformed Early Cretaceous-Paleocene carbonatic and volcanic succes-sions, as well as rare Carboniferous, Permian and Jurassic slices of platform limestones (Hunziker et al., 2015). The Durkan Complex is commonly interpreted as representing the disrupted sedimentary cover of the passive margin of a micro-continent known in literature as the Bajgan-Durkan Complex. However, its stratigraphic succession, as well as the age and geochemistry of the volcanic rocks are still poorly known. Nevertheless, such data are fundamental for constraining its meaning for the pre-Eocene geodynamic evolution of the Makran Accretionary Prism.

We present new geological, stratigraphic, biostratigraphic data on the sedimentary and meta-sedimen-tary successions as well as new geochemical data on the associated volcanic and meta-volcanic rocks cropping out in the western sector of the Durkan Complex (i.e., in the Manujan area, Figs. 2, 3). These data are fundamental to define the tectono-stratigraphic architecture of the western Durkan Complex and they can provide robust constraint for understanding the significance of the Durkan Complex for the geodynamic evolution of the Makran Accretionary Prism

NEW FIELD DATAWe had investigated in detail the tectono-stratigraphic architecture of the western Durkan Complex by stu-dying four key transects in which different stratigraphic successions are well preserved within distinct tectonic slices (Fig. 4). These slices are charcaterized by showing both slightly metamorphic and non-metamorphic highly-deformed stratigraphic successions.

GEOCHEMISTRYVolcanic rocks in all the transects show very similar geochemical features. They mainly consist of alkaline basalts and minor trachybasalts showing high Nb/Y ratios (0.62 – 4.4). According to the REE abundance (Sun & McDonough, 1989) we distin-guished three groups of rocks showing marked but different enrichment of LREE and MREE with respect to HREE (Fig. 6). In the ThN vs NbN discrimination diagram (Fig. 7) they plot in the field for P-MORB and Alkaline basalt from subduction unrela-ted setting. These rocks have Zr and Th/Ta ratios similar to those of Oceanic Island Basalt rather than those of continental margin settings (Fig. 8). These geochemical features indicates an enriched mantle source for the volcanic rocks of the Durkan Complex (e.g., Safonova et al., 2016).

BIOSTRATIGRAPHYBiostratigraphic analysis were aimed to date the sedimentary rocks associated with the volcanic rocks, in order to provi-de age constraints for the magmatic activity. The biostratigraphy is based on the integration of foraminifera, radiolarians and calcareous nannofossils. The results are shown in Figure 9.

CONCLUSIONIn summary, our data indicate that the western Durkan Complex successions have recorded complex Late Cretaceous interplay of sedimentation and alkaline magmatism, which is significantly younger than the Middle Jurassic - Early Creta-ceous rifting stages recognized in literature in the eastern Durkan Complex.The distinct successions of the Durkan Complex show tectono-stratigraphic features that can be reconciled to the cap (Figs. 4b, 4e4), the slope (Figs. 4d1, 4d2, 5e2, 5e5), and the foothill (Figs. 4c3, 4d3) of a typical seamount environ-ment. Finally, our new findings and regional-scale comparisons suggest that the Late Cretaceous alkaline magmatic pulse recorded in the Durkan Complex was likely related to mantle plume activity in the Makran sector of the Neotethys.

REFERENCESBarbero, E., Delavari, M., Dolati, A., Saccani, E., Marroni, M., Catanzariti, R., Pandolfi, L., 2020. The Ganj Complex reinterpreted as a Late Cretaceous volcanic arc: Implications for the geodynamic evolution of the North Makran domain (southeast Iran). Journal of Asian Earth Science. https://doi.or-g/10.1016/j.jseaes.2020.104306.Burg, J.-P., 2018. Geology of the onshore Makran accretionary wedge: Synthesis and tectonic interpretation. Earth-Science Reviews 185, 1210-1231. https://doi.org/10.1016/j.earscirev.2018.09.011.Hunziker, D., Burg, J.-P., Bouilhol, P., von Quadt, A., 2015. Jurassic rifting at the Eurasian Tethys margin: Geochemical and geochronological constraints from granitoids of North Makran, southeastern Iran. Tectonics 34, 571-593. 10.1002/2014TC003768McCall, G.J.H., Kidd, R.G,W., 1982. The Makran southeastern Iran: the anatomy of a convergent margin active from Cretaceous to present. In: Leggett, J.K. (Ed.), Trench-forearc geology: sedimentation and tectonics of modern and ancient plate margins, Geological Society of London Special Publications vol. 10, pp. 387-397.Saccani, E., 2015. A new method of discriminating different types of post-Archean ophiolitic basalts and their tectonic significance using Th-Nb and Ce-Dy-Yb systematics. Geoscience Frontiers 6, 481-501. 10.1016/j.gsf.2014.03.006Saccani, E., Delavari, M., Dolati, A., Marroni, M., Pandolfi, L., Chiari, M., Barbero E., 2018. New insights into the geodynamics of Neo-Tethys in the Makran area: Evidence from age and petrology of ophiolites from the Coloured Mélange Complex (SE Iran). Gondwana Research 62, 306-327. 10.1016/j.-gr.2017.07.013Safonova, I., Maruyama, S., Kojima, S., Komiya, T., Krivonogov, S., Koshida, K., 2016. Recognizing OIB and MORB in accretionary complexes: A new approach based on ocean plate stratigraphy, petrology and geochemistry. Gondwana Research 33, 92–114. https://doi.org/10.1016/j.gr.2015.06.013Samimi Namin, M., 1983. Geological Map of Minab 1:250000 Scale. Tehran: Ministry of Mines and Metal, Geological Survey of Iran.Sun, S.S., McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saun-ders, A.D., Norry, M.J. (Eds.), Magmatism in the Ocean Basins, Geological Society of London Special Publication vol. 42, pp. 313-345.

INTRODUCTION AND GEOLOGICAL SETTINGThe Makran Accretionary Prism is an E-W trending accretionary prism in the SE of Iran that is bounded by two strike-slip fault systems (Fig.1). The Makran has resulted from the Cretaceous to present-day convergence between the Arabian and Eurasian plates that was accomodated by the northward subduction of the Neo-Tethys Ocean beneath the southern margin of Eurasia (McCall & Kidd, 1982; Burg, 2018). This subduction is still active beneath the Makran in the Oman Gulf (Fig.1).

Figure 1

Tectonic scheme of the Makran (modified after Burg, 2018)

Figure 2 Tectonic scheme of the western Makran (from Barbero et al., 2020)

Figure 3 Geological scheme of the studied area (modified from Samimi Namim, 1983)

Figure 4 Schematic stratigraphic-structural setting and stratigraphic columns for the suc-cessions in the studied transects

Figure 5 Field occurences of the Durkan Complex in the studied transects:a) foliated meta-volcaniclastic arenites; b) massive marble; c) panoramic view of the contact between the Volcano-Sedimentary Sequence (VSS) and the Massive Limestone (ml) lithostrati-graphic units; d) primary stratigraphic relationships between lavas and pelagic sedimentary rocks; e) volcanic rocks in the Volcanic Sequence; f) thin bedded limestones alternating with shaly-marls (Limestone and Shale); g) massive volcanic rocks alternated with volcaniclastic arenites from the Volcanic Sequence; h) matrix-supported breccia from the Volcano-Sedimentary Sequence showing limestone and shale clasts in a fine-grained greyish to greenish matrix;

Figure 6 Chondrite-normalized REE patterns for magmatic rocks from the western Durkan Com-plex. Normalizing values are from Sun and McDonough (1989).

Figure 7

N-MORB normalized Th vs. Nb discri-mination diagram of Saccani (2015)

Figure 8

Zr vs. Th/Ta diagram for the magmatic rocks of the western Durkan Complex

Figure 9

Summary of the results of the biostratigraphic analyses