The Sabzevar blueschists of the North-Central Iranian micro-continent as remnants of the Neotethys-related oceanic crust subduction

Omrani, Hadi; Moazzen, Mohssen; Oberhänsli, Roland; Altenberger, Uwe; Lange, Manuela

doi:10.1007/s00531-013-0881-9

Cited by 40 publications

(28 citation statements)

References 55 publications

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“…Lastly, a minor cluster of 115-to 80-Ma metabasic and metapelitic detrital rutiles are found in the Kashghan Formation and may reflect derivation from eclogite to amphibolite facies rocks associated with Cretaceous intraoceanic subduction (Figure 9). Cretaceous high-pressure metamorphic rocks have been documented in the Kermanshah complex but have been previously described along strike in the Neyriz ophiolite complex (southwestern Iran) and in Oman (Agard et al, 2010;Omrani et al, 2013).…”

Section: 1029/2019gc008185mentioning

confidence: 99%

The Proto‐Zagros Foreland Basin in Lorestan, Western Iran: Insights From Multimineral Detrital Geothermochronometric and Trace Elemental Provenance Analysis

Barber

Stöckli

Galster

2019

Geochem Geophys Geosyst

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Detrital zircon (DZ) U‐Pb geochronology is a widely used provenance tool that leverages bedrock age signatures of hinterland source terranes. However, complex sediment recycling of multicycle zircon and hinterland provinces with nondiagnostic U‐Pb ages represent possible pitfalls for provenance reconstructions. Additional biases pertain to source rock zircon fertilities and insensitivity to low‐ and medium‐grade tectonothermal events that do not result in zircon generation. To bridge these inherent biases and gaps in DZ U‐Pb provenance data sets and derive more comprehensive tectonic reconstruction, this study combined U‐Pb and trace element analyses on DZ, apatite, and rutile as well as zircon (U‐Th)/He analyses from the Proto‐Zagros foreland basin in western Iran to shed light on Late Cretaceous tectonic accretion along Arabia. Integrated multimineral, multimethod data sets record formation of a 110‐ to 85‐Ma island arc within Triassic mid‐oceanic ridge crust of the Neotethys ocean, simultaneous obduction starting in Santonian‐Early Campanian times, and inversion of the Arabian rift margin. Overall, integration of these techniques constrains provenance based on multiple independent criteria including crystallization age, cooling history, and petrogenic‐geodynamic environment. This approach not only more completely described provenance signatures but also helped avoid significant pitfalls. For example, while Triassic DZ U‐Pb ages might be mistaken as input from Eurasia, zircon trace element analysis reveals a MORB signature and attributes these DZ to Neotethyan oceanic rather than Eurasian continental origin, having fundamentally different paleogeographic/tectonic implications for the Arabia‐Eurasia collision. Moreover, detrital rutile and apatite resolve and characterize multiple Paleozoic‐Mesozoic thermotectonic events not recorded by DZ U‐Pb due to their largely amagmatic nature.

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Section: 1029/2019gc008185mentioning

confidence: 99%

The Proto‐Zagros Foreland Basin in Lorestan, Western Iran: Insights From Multimineral Detrital Geothermochronometric and Trace Elemental Provenance Analysis

Barber

Stöckli

Galster

2019

Geochem Geophys Geosyst

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“…The STHO comprises four main regions where ophiolites crop out (Fig. 3), separated by the Paleocene-Eocene Oryan sedimentary basin: (1) NNW of Sabzevar (the Sabzevar ophiolite, studied by (Moghadam et al, 2014b;Moghadam et al, 2015;Nasrabady et al, 2011;Omrani et al, 2013;Rossetti et al, 2014;Rossetti et al, 2010;Shojaat et al, 2003)); (2) SSW of Sabzevar (Oryan ophiolite, no published data); (3) Cheshmehshir in the far south (Maghfouri et al, 2016), and (4) north of Torbat-e-Heydarieh, the focus of this study.…”

Section: Geological Settingmentioning

confidence: 99%

“…4-OIB-type lavas are present in Sabzevar (Moghadam et al, 2014a) but are absent in the THO, although the latter contains minor E-MORB. 5-The Sabzevar ophiolite marks an orogenic suture, with a Paleocene HP/LT metamorphic core (Omrani et al, 2013;Rossetti et al, 2014) and an external thrust-and-fold belt, showing evidence of a ductile-to-brittle top-to-the-SSE sense of tectonic transport (Rossetti et al, 2014). Moreover, a HP granulite event, Albian in age, may exist in the Sabzevar zone (Nasrabady et al, 2011;Rossetti et al, 2010).…”

Section: Tectonic Setting Of the Torbat-e-heydarieh Ophiolitementioning

confidence: 99%

Subduction initiation and back-arc opening north of Neo-Tethys: Evidence from the Late Cretaceous Torbat-e-Heydarieh ophiolite of NE Iran

et al. 2019

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How new subduction zones form is an ongoing scientific question with key implications for our understanding of how this process influences the behavior of the overriding plate. Here we focus on the effects of a Late Cretaceous subduction-initiation (SI) event in Iran and show how SI caused enough extension to open a back-arc basin in NE Iran. The Late Cretaceous Torbat-e-Heydarieh ophiolite (THO) is well exposed as part of the Sabzevar-Torbat-e-Heydarieh ophiolite belt. It is dominated by mantle peridotite, with a thin crustal sequence. The THO mantle sequence consists of harzburgite, clinopyroxene-harzburgite, plagioclase lherzolite, impregnated lherzolite, and dunite. Spinel in THO mantle peridotites show variable Cr# (10–63), similar to both abyssal and fore-arc peridotites. The igneous rocks (gabbros and dikes intruding mantle peridotite, pillowed and massive lavas, amphibole gabbros, plagiogranites and associated diorites, and diabase dikes) display rare earth element patterns similar to MORB, arc tholeiite and back-arc basin basalt. Zircons from six samples, including plagiogranites and dikes within mantle peridotite, yield U-Pb ages of ca. 99–92 Ma, indicating that the THO formed during the Late Cretaceous and was magmatically active for ∼7 m.y. THO igneous rocks have variable εNd(t) of +5.7 to +8.2 and εHf(t) ranging from +14.9 to +21.5; zircons have εHf(t) of +8.1 to +18.5. These isotopic compositions indicate that the THO rocks were derived from an isotopically depleted mantle source similar to that of the Indian Ocean, which was slightly affected by the recycling of subducted sediments. We conclude that the THO and other Sabzevar-Torbat-e-Heydarieh ophiolites formed in a back-arc basin well to the north of the Late Cretaceous fore-arc, now represented by the Zagros ophiolites, testifying that a broad region of Iran was affected by upper-plate extension accompanying Late Cretaceous subduction initiation.

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“…Northern Iran ophiolites and high‐pressure and low‐temperature (HP‐LT) metamorphic rocks (along Alborz Mountain ranges; Omrani et al ., ) are considered as Palaeotethys and the other ophiolites [along Zagros, Eastern Iran Zone and around Central Iranian Micro‐continental blocks (CIM)] are considered as Neotethys suture zones respectively (e.g. Shafaii Moghadam & Stern, ; Omrani et al ., ).…”

Section: Introductionmentioning

confidence: 97%

“…Northern Iran ophiolites and high-pressure and low-temperature (HP-LT) metamorphic rocks (along Alborz Mountain ranges; Omrani et al, 2013a) are considered as Palaeotethys and the other ophiolites [along Zagros, Eastern Iran Zone and around Central Iranian Micro-continental blocks (CIM)] are considered as Neotethys suture zones respectively (e.g. Shafaii Moghadam & Stern, 2011;Omrani et al, 2013b). Kopp et al 2000 described the Makran Accretionary Prism (MAP) as one of the largest subduction accretions on Earth (400-600 km from the deformation front in the Gulf of Oman to the Baluchistan volcanic arc), that is located at the southern CIM.…”

Section: Introductionmentioning

confidence: 99%

Iranshahr blueschist: subduction of the inner Makran oceanic crust

Omrani

Moazzen

Oberhänsli

et al. 2016

Journal Metamorphic Geology

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The Makran accretionary prism in SE Iran and SW Pakistan is one of the most extensive subduction accretions on Earth. It is characterized by intense folding, thrust faulting and dislocation of the Cenozoic units that consist of sedimentary, igneous and metamorphic rocks. Rock units forming the northern Makran ophiolites are amalgamated as a mélange. Metamorphic rocks, including greenschist, amphibolite and blueschist, resulted from metamorphism of mafic rocks and serpentinites. In spite of the geodynamic significance of blueschist in this area, it has been rarely studied. Peak metamorphic phases of the northern Makran mafic blueschist in the Iranshahr area are glaucophane, phengite, quartz±omphacite+epidote. Post peak minerals are chlorite, albite and calcic amphibole. Blueschist facies metasedimentary rocks contain garnet, phengite, albite and epidote in the matrix and as inclusions in glaucophane. The calculated P–T pseudosection for a representative metabasic glaucophane schist yields peak pressure and temperature of 11.5–15 kbar at 400–510 °C. These rocks experienced retrograde metamorphism from blueschist to greenschist facies (350–450 °C and 7–8 kbar) during exhumation. A back arc basin was formed due to northward subduction of Neotethys under Eurasia (Lut block). Exhumation of the high‐pressure metamorphic rocks in northern Makran occurred contemporarily with subduction. Several reverse faults played an important role in exhumation of the ophiolitic and HP‐LT rocks. The presence of serpentinite shows the possible role of a serpentinite diapir for exhumation of the blueschist. A tectonic model is proposed here for metamorphism and exhumation of oceanic crust and accretionary sedimentary rocks of the Makran area. Vast accretion of subducted materials caused southward migration of the shore.

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The Sabzevar blueschists of the North-Central Iranian micro-continent as remnants of the Neotethys-related oceanic crust subduction

Cited by 40 publications

References 55 publications

The Proto‐Zagros Foreland Basin in Lorestan, Western Iran: Insights From Multimineral Detrital Geothermochronometric and Trace Elemental Provenance Analysis

The Proto‐Zagros Foreland Basin in Lorestan, Western Iran: Insights From Multimineral Detrital Geothermochronometric and Trace Elemental Provenance Analysis

Subduction initiation and back-arc opening north of Neo-Tethys: Evidence from the Late Cretaceous Torbat-e-Heydarieh ophiolite of NE Iran

Iranshahr blueschist: subduction of the inner Makran oceanic crust

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