Moghadam, Hadi Shafaii, Stern, R. J., Griffin, W. L., Khedr, M. Z., Kirchenbaur, M., Ottley, C. J., Whattam, S. A., Kimura, J-, I, Ghorbani, G., Gain, S., O'Reilly, S. Y. and Tamura, A. (2020). Subduction initiation and back-arc opening north of Neo-Tethys: Evidence from the Late Cretaceous Torbat-e-Heydarieh ophiolite of NE Iran. Geol. Soc. Am. Bull., 132 (5-6). S. 1083 - 1106. BOULDER: GEOLOGICAL SOC AMER, INC. ISSN 1943-2674

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Abstract

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-harz burgite, 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 similar to 7 m.y. THO igneous rocks have variable epsilon Nd(t) of +5.7 to +8.2 and epsilon Hf(t) ranging from +14.9 to +21.5; zircons have epsilon Hf(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.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Moghadam, Hadi ShafaiiUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Stern, R. J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Griffin, W. L.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Khedr, M. Z.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Kirchenbaur, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Ottley, C. J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Whattam, S. A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Kimura, J-, IUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Ghorbani, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Gain, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
O'Reilly, S. Y.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Tamura, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-335552
DOI: 10.1130/B35065.1
Journal or Publication Title: Geol. Soc. Am. Bull.
Volume: 132
Number: 5-6
Page Range: S. 1083 - 1106
Date: 2020
Publisher: GEOLOGICAL SOC AMER, INC
Place of Publication: BOULDER
ISSN: 1943-2674
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
ZIRCON U-PB; REGION CENTRAL IRAN; SISTAN SUTURE ZONE; ISLAND-ARC; GEODYNAMIC EVOLUTION; SABZEVAR OPHIOLITE; TECTONIC EVOLUTION; GEOCHEMICAL CONSTRAINTS; NEOTETHYAN SUBDUCTION; OCEANIC LITHOSPHEREMultiple languages
Geosciences, MultidisciplinaryMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/33555

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