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U-Pb zircon geochronology of late Neoproterozoic-Early Cambrian granitoids in Iran: Implications for paleogeography, magmatism, and exhumation history of Iranian basement

Hassanzadeh, Jamshid and Stockli, Daniel F. and Horton, Brian K. and Axen, Gary J. and Stockli, Lisa D. and Grove, Marty and Schmitt, Axel K. and Walker, J. Douglas (2008) U-Pb zircon geochronology of late Neoproterozoic-Early Cambrian granitoids in Iran: Implications for paleogeography, magmatism, and exhumation history of Iranian basement. Tectonophysics, 451 (1-4). pp. 71-96. ISSN 0040-1951.

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Eurasia has largely grown to its present enormous size through episodic addition of crustal blocks by recurring birth and demise of oceans such as Paleotethys and Neotethys. Excluding the Kopet Dagh Mountains in the northeast, crystalline basement rocks of various dimensions are exposed in all continental tectonic zones of Iran. These rocks have traditionally been viewed as continental fragments with Gondwanan affinity and summarily been assigned Precambrian or younger ages, despite the fact that evidence from isotopic dating has largely been lacking. This study presents new ion microprobe and thermal-ionization zircon U-Pb geochronological data from granitoids and orthogneisses from several locations in central Iran and the Sanandaj–Sirjan structural zones to determine crystallization ages and investigate the origin and continental affinity of these various crustal fragments. The resulting U-Pb crystallization ages for the granites and orthogneisses range from late Neoproterozoic to Early Cambrian, matching the mostly juvenile Arabian–Nubian shield and Peri-Gondwanan terranes constructed after the main phase of Pan-African orogenesis. TIMS analyses of zircons with inherited cores from western Iran suggest that the Neoproterozoic crust of Iran might not be entirely juvenile, pointing to the potential presence of inherited older Proterozoic components as is common in the eastern Arabian shield. More importantly, the new zircon U-Pb crystallization ages unequivocally demonstrate that crystalline basement underlying the Sanandaj–Sirjan zone, central Iran, and the Alborz Mountains is composed of continental fragments with Gondwanan affiliation, characterized by wide spread late Neoproterozoic subduction-related magmatism. The exposure of these late Neoproterozoic–Early Cambrian basement rocks in the Iranian regions north of the Zagros is structurally controlled and linked to both large-scale crustal extension and exhumation during Mesozoic and Tertiary time as well as Tertiary collisional tectonics associated with the closure of Neotethys.

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Additional Information:© 2008 Published by Elsevier B.V. Received 15 October 2007; accepted 6 November 2007 Available online 15 December 2007. This research was supported by Research Council of University of Tehran awarded to Hassanzadeh and National Science Foundation (grant EAR-0337775 to Horton and Axen) and (grant EAR-9902932 to Axen). We thank Dr. Mohammad Sadegh Fakhr for identifying plant fossils, Roghieh Akbar Ashrafi, Safia Omidian, Ahmad Reza Malekpour and Morteza Pirooz for help with figures, and David Gingrich, Jesse Mosolf, and Terrence Dewane for assistance with ion-microprobe and TIMS analyses. Extensive comments by reviewers Jahandar Ramezani and Gerard Stampfli, and editors Ezat Heydari and Rasoul Sorkhabi contributed greatly to the improvement of this text. The ion microprobe facility at UCLA is partly supported by a grant from the Instrumentation and Facilities Program, Division of Earth Sciences, National Science Foundation.
Funding AgencyGrant Number
Research Council of University of TehranUNSPECIFIED
NSF Division of Earth Sciences Instrumentation and Facilities ProgramUNSPECIFIED
Subject Keywords:U-Pb dating; Zircon; Gondwana; Doran granite; Exhumation; Continental basement
Issue or Number:1-4
Record Number:CaltechAUTHORS:20130820-143709614
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Official Citation:Jamshid Hassanzadeh, Daniel F. Stockli, Brian K. Horton, Gary J. Axen, Lisa D. Stockli, Marty Grove, Axel K. Schmitt, J. Douglas Walker, U-Pb zircon geochronology of late Neoproterozoic–Early Cambrian granitoids in Iran: Implications for paleogeography, magmatism, and exhumation history of Iranian basement, Tectonophysics, Volume 451, Issues 1–4, 28 April 2008, Pages 71-96, ISSN 0040-1951,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40744
Deposited By: Tony Diaz
Deposited On:20 Aug 2013 22:46
Last Modified:03 Oct 2019 05:42

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