Dextral transpression in Late Cretaceous continental collision, Sanandaj–Sirjan Zone, western Iran

Mohajjel, Mohammad; Fergusson, C. L.

doi:10.1016/s0191-8141(00)00023-7

Cited by 319 publications

(166 citation statements)

References 22 publications

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“…Following Stocklin (1968), several geologists consider the SSZ as a once-active margin of the Central Iranian block (e.g. Berberian & King, 1981;Sengor, 1990;Sheikholeslami et al 2008;Fazlnia et al 2009) with northeastward subduction of the Tethys Ocean during Late Triassic-Early Jurassic time (Berberian & King, 1981;Davoudzadeh & Schmidt, 1984) or Late Jurassic time (Mohajjel & Fergusson, 2000). Others suppose that the SSZ is an accreted microcontinent that separated from Gondwanaland during Early Jurassic time (e.g.…”

Section: D Sanandaj-sirjan Zonementioning

confidence: 99%

Geodynamic evolution of Upper Cretaceous Zagros ophiolites: formation of oceanic lithosphere above a nascent subduction zone

2011

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-The Zagros fold-and-thrust belt of SW Iran is a young continental convergence zone, extending NW-SE from eastern Turkey through northern Iraq and the length of Iran to the Strait of Hormuz and into northern Oman. This belt reflects the shortening and off-scraping of thick sediments from the northern margin of the Arabian platform, essentially behaving as the accretionary prism for the Iranian convergent margin. Distribution of Upper Cretaceous ophiolites in the Zagros orogenic belt defines the northern limit of the evolving suture between Arabia and Eurasia and comprises two parallel belts: (1) Outer Zagros Ophiolitic Belt (OB) and (2) Inner Zagros Ophiolitic Belt (IB). These belts contain complete (if disrupted) ophiolites with well-preserved mantle and crustal sequences. Mantle sequences include tectonized harzburgite and rare ultramafic-mafic cumulates as well as isotropic gabbro lenses and isolated dykes within the harzburgite. Crustal sequences include rare gabbros (mostly in IB ophiolites), sheeted dyke complexes, pillowed lavas and felsic rocks. All Zagros ophiolites are overlain by Upper Cretaceous pelagic limestone. Limited radiometric dating indicates that the OB and IB formed at the same time during Late Cretaceous time. IB and OB components show strong suprasubduction zone affinities, from mantle harzburgite to lavas. This is shown by low whole-rock Al 2 O 3 and CaO contents and spinel and orthopyroxene compositions of mantle peridotites as well as by the abundance of felsic rocks and the trace element characteristics of the lavas. Similarly ages, suprasubduction zone affinities and fore-arc setting suggest that the IB and OB once defined a single tract of fore-arc lithosphere that was disrupted by exhumation of subducted Sanandaj-Sirjan Zone metamorphic rocks. Our data for the OB and IB along with better-studied ophiolites in Cyprus, Turkey and Oman compel the conclusion that a broad and continuous tract of fore-arc lithosphere was created during Late Cretaceous time as the magmatic expression of a newly formed subduction zone developed along the SW margin of Eurasia.

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Section: D Sanandaj-sirjan Zonementioning

confidence: 99%

Geodynamic evolution of Upper Cretaceous Zagros ophiolites: formation of oceanic lithosphere above a nascent subduction zone

2011

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“…However, a key point is that the precise time of collision between Arabia and Eurasia is still controversial. Age estimates for the onset of collision are varied: Late Cretaceous (Stocklin, 1974;Berberian & King, 1981;Alavi, 1994;Mohajjel & Fergusson, 2000) to Eocene (Ghasemi & Talbot, 2006;M. Aghazadeh, unpub. Ph.D. thesis, Tarbiat Modares Univ., 2009), EoceneOligocene (Hooper et al 1994;Horton et al 2008), Oligocene (Yilmaz, 1993), Miocene (Stoneley, 1981;Sengör & Natal'in, 1996;Robertson, 2000;Mohajjel, Fergusson & Sahandi, 2003;McQuarrie et al 2003) and Pliocene (Philip et al 1989).…”

Section: Outline Of Regional Geologymentioning

confidence: 99%

Post-collisional polycyclic plutonism from the Zagros hinterland: the Shaivar Dagh plutonic complex, Alborz belt, Iran

et al. 2011

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-The petrological and geochronological study of the Cenozoic Shaivar Dagh composite intrusion in the Alborz Mountain belt (NW Iran) reveals important clues to decipher complex relations between magmatic and tectonic processes in the central sectors of the Tethyan (Alpine-Himalayan) orogenic belt. This pluton is formed by intrusion at different times of two main magmatic cycles. The older (Cycle 1) is formed by calc-alkaline silicic rocks, which range in composition from diorites to granodiorites and biotite granites, with abundant mafic microgranular enclaves. The younger cycle (Cycle 2) is formed by K-rich monzodiorite and monzonite of marked shoshonitic affinity. The latter form the larger volumes of the exposed plutonic rocks in the studied complex. Zircon geochronology (laser ablation ICP-MS analyses) gives a concordia age of 30.8 ± 2.1 Ma for the calc-alkaline rocks (Cycle 1) and a range from 23.3 ± 0.5 to 25.1 ± 0.9 Ma for the shoshonitic association (Cycle 2). Major and trace element relations strongly support distinct origins for each magmatic cycle. Rocks of Cycle 1 have all the characteristic features of active continental margins. Shoshonitic rocks (Cycle 2) define two continuous fractionation trends: one departing from a K-rich basaltic composition and the other from an intermediate, K-rich composition. A metasomatized-mantle origin for the two shoshonitic series of Cycle 2 is proposed on the basis of comparisons with experimental data. The origin of the calc-alkaline series is more controversial but it can be attributed to processes in the suprasubduction mantle wedge related to the incorporation of subducted mélanges in the form of silicic cold plumes. A time sequence can be established for the processes responsible of the generation of the two magmatic cycles: first a calc-alkaline cycle typical of active continental margins, and second a K-rich cycle formed by monzonites and monzodiorites. This sequence precludes the younger potassic magmas as precursors of the older calc-alkaline series. By contrast, the older calc-alkaline magmas may represent the metasomatic agents that modified the mantle wedge during the last stages of subduction and cooked a fertile mantle region for late potassic magmatism after continental collision.

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“…The Zagros orogenic belt resulted from the collision of the African -Arabian continent and the Iranian microcontinent (Berberian & King 1981;Alavi 1994;Mohajjel & Fergusson 2000;Agard et al 2005Agard et al , 2011Hafkenscheid et al 2006). The Dorud-Azna region is situated in the central part of the SSZ close to the Main Zagros thrust.…”

Section: Geological Settingmentioning

confidence: 99%

“…Ages given in Ma: Data sources: (1) Shakerardakani et al 2015;(2) Fergusson et al 2016. Map is updated and modified after Mohajjel & Fergusson (2000). b -Orientation of mafic dykes in the Galeh-Doz orthogneiss: alkaline trend mostly WNW-ESE with a variable dip angle whereas subalkaline dykes seem to trend ENE-WSW or NNE-SSW (great circles, 21 data).…”

Section: Geological Settingmentioning

confidence: 99%

Geochemical and isotopic evidence for Carboniferous rifting: mafic dykes in the central Sanandaj-Sirjan zone (Dorud-Azna, West Iran)

Shakerardakani¹,

Neubauer²,

Bernroider³

et al. 2017

Geologica Carpathica

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Abstract:In this paper, we present detailed field observations, chronological, geochemical and Sr-Nd isotopic data and discuss the petrogenetic aspects of two types of mafic dykes, of alkaline to subalkaline nature. The alkaline mafic dykes exhibit a cumulate to foliated texture and strike NW-SE, parallel to the main trend of the region. The 40 Ar/ 39 Ar amphibole age of 321.32 ± 0.55 Ma from an alkaline mafic dyke is interpreted as an indication of Carboniferous cooling through ca. 550 °C after intrusion of the dyke into the granitic Galeh-Doz orthogneiss and Amphibolite-Metagabbro units, the latter with Early Carboniferous amphibolite facies grade metamorphism and containing the Dare-Hedavand metagabbro with a similar Carboniferous age. The alkaline and subalkaline mafic dykes can be geochemically categorized into those with light REE-enriched patterns [(La/Yb) N = 8.32-9.28] and others with a rather flat REE pattern [(La/Yb) N = 1.16] and with a negative Nb anomaly. Together, the mafic dykes show oceanic island basalt to MORB geochemical signature, respectively. This is consistent, as well, with the (Tb/Yb) PM ratios. The alkaline mafic dykes were formed within an enriched mantle source at depths of ˃ 90 km, generating a suite of alkaline basalts. In comparison, the subalkaline mafic dykes were formed within more depleted mantle source at depths of ˂ 90 km. The subalkaline mafic dyke is characterized by 87 Sr/ 86 Sr ratio of 0.706 and positive ɛ Nd (t) value of + 0.77, whereas 87 Sr/ 86 Sr ratio of 0.708 and ɛ Nd (t) value of + 1.65 of the alkaline mafic dyke, consistent with the derivation from an enriched mantle source. There is no evidence that the mafic dykes were affected by significant crustal contamination during emplacement. Because of the similar age, the generation of magmas of alkaline mafic dykes and of the Dare-Hedavand metagabbro are assumed to reflect the same process of lithospheric or asthenospheric melting. Carboniferous back-arc rifting is the likely geodynamic setting of mafic dyke generation and emplacement. In contrast, the subalkaline mafic sill is likely related to the emplacement of the Jurassic Darijune gabbro.

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Dextral transpression in Late Cretaceous continental collision, Sanandaj–Sirjan Zone, western Iran

Cited by 319 publications

References 22 publications

Geodynamic evolution of Upper Cretaceous Zagros ophiolites: formation of oceanic lithosphere above a nascent subduction zone

Geodynamic evolution of Upper Cretaceous Zagros ophiolites: formation of oceanic lithosphere above a nascent subduction zone

Post-collisional polycyclic plutonism from the Zagros hinterland: the Shaivar Dagh plutonic complex, Alborz belt, Iran

Geochemical and isotopic evidence for Carboniferous rifting: mafic dykes in the central Sanandaj-Sirjan zone (Dorud-Azna, West Iran)

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