the durkan complex in the western makran accretionary ... · tary successions as well as new...
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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
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