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Age revision of the Neotethyan arc migration into the southeast Urumieh-Dokhtar belt of Iran: Geochemistry and U–Pb zircon geochronology

Hosseini, Mohammad Reza and Hassanzadeh, Jamshid and Alirezaei, Saeed and Sun, Weidong and Li, Cong-Ying (2017) Age revision of the Neotethyan arc migration into the southeast Urumieh-Dokhtar belt of Iran: Geochemistry and U–Pb zircon geochronology. Lithos, 284-285 . pp. 296-309. ISSN 0024-4937. doi:10.1016/j.lithos.2017.03.012.

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The Urumieh-Dokhtar magmatic belt of Central Iran runs parallel to the Zagros orogenic belt and has been resulted from Neotethys ocean subduction underneath Eurasia. The Bahr Aseman volcanic-plutonic complex (BAC), covering an area ~ 2000 km^2 in the Kerman magmatic belt (KMB) in the southern section of the Urumieh-Dokhtar belt, has long been considered as the earliest manifestation of extensive Cenozoic arc magmatism in KMB. The nature and timing of the magmatism, however, is poorly constrained. An area ~ 1000 km^2, in BAC and adjacent Razak volcaniclastic complex and Jebal Barez-type granitoids, was mapped and sampled for geochemistry and geochronology. Andesite and basaltic andesite are the main volcanic components in the study area; plutonic bodies vary from tonalite to quartz diorite, granodiorite and biotite-granite. The rocks in BAC display dominantly normal calc-alkaline character. On spider diagrams, the rocks are characterized by enrichments in LILE relative to HFSE and enrichments in LREE relative to HREE. These features suggest a subduction related setting for the BAC. La_N/Yb_N ratios for the intrusive and volcanic rocks range from 1.41 to 5.16 and 1.01 to 6.42, respectively. These values are lower than those for other known granitoids in KMB, namely the abyssal, dominantly Oligocene Jebal Barez-type (La_N/Yb_N = 1.66–9.98), and the shallow, dominantly late Miocene Kuh Panj-type (La_N/Yb_N = 12.97–36.04) granitoids. This suggests a less evolved magma source for the BAC igneous rocks. In Y vs. Nb and Th/Yb vs. La/Yb discrimination diagrams, an island-arc setting is defined for the BAC rocks. The rocks further plot in primitive island-arc domain in Nb vs. Rb/Zr and Y/Nb vs. TiO_2 diagrams. The BAC volcanic and plutonic rocks yielded zircon U–Pb ages of 78.1 to 82.7 Ma and 77.5 to 80.8 Ma, respectively. Zircon U–Pb dating of volcanic rocks and granitoids from the adjacent Razak complex and the Jebal Barez-type granitoids indicated 48.2 Ma and 26.1 Ma ages, respectively, consistent with earlier works on similar rocks elsewhere in KMB. The new data allow a revision of the chronostratigraphy/tectonic history of KMB. In Late Cretaceous, a back arc rift developed extending from Nain to Baft (NB back arc) to the northeast of the Sanandaj-Sirjan magmatic arc. Along with shrinking of the Neotethys Ocean, the dip angle of the subducting slab decreased during the Late Cretaceous, and arc magmatism moved from the Sanandaj-Sirjan zone landward. Meanwhile, Bahr Aseman volcanic-plutonic complex formed as an island-arc in NB back arc rift. Later with arc shift, due to shallowing of subducted slab, magmatism moved toward continent leading to extensive volcanism in Kerman magmatic arc during Eocene and Oligocene, represented by volcanic-sedimentary Razak and Hezar Complexes, respectively.

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Additional Information:© 2017 Elsevier B.V. Received 14 August 2016, Accepted 12 March 2017, Available online 25 March 2017. We are grateful to the National Iranian Copper Industries Company (NICICO), in particular the Exploration and Research and Development Departments, for their support. Mineralogy and Metallogeny group of Guangzhou Institute of Geochemistry is thanked for assistance in chemical and radioisotope analyses. U–Pb dating was supported by NSFC grant No. 91328204 to Prof. Weidong Sun. We thank Dr. Abbas Sadeghi, Shahid Beheshti University, Iran, for paleontology studies.
Funding AgencyGrant Number
National Natural Science Foundation of China91328204
Subject Keywords:Neotethys; Urumieh-Dokhtar; Kerman belt; Bahr Aseman; Island-arc; Zircon U–Pb dating
Record Number:CaltechAUTHORS:20170803-073314908
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Official Citation:Mohammad Reza Hosseini, Jamshid Hassanzadeh, Saeed Alirezaei, Weidong Sun, Cong-Ying Li, Age revision of the Neotethyan arc migration into the southeast Urumieh-Dokhtar belt of Iran: Geochemistry and U–Pb zircon geochronology, Lithos, Volumes 284–285, July 2017, Pages 296-309, ISSN 0024-4937, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79809
Deposited By: Tony Diaz
Deposited On:05 Aug 2017 21:02
Last Modified:15 Nov 2021 17:50

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