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Large-magnitude continental extension in the northeastern Iranian Plateau: Insight from K-feldspar ^(40)Ar/^(39)Ar thermochronology from the Shotor Kuh–Biarjmand metamorphic core complex

Malekpour-Alamdari, Ahmadreza and Axen, Gary and Heizler, Matthew and Hassanzadeh, Jamshid (2017) Large-magnitude continental extension in the northeastern Iranian Plateau: Insight from K-feldspar ^(40)Ar/^(39)Ar thermochronology from the Shotor Kuh–Biarjmand metamorphic core complex. Geosphere, 13 (4). pp. 1207-1233. ISSN 1553-040X. https://resolver.caltech.edu/CaltechAUTHORS:20170620-161806951

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Abstract

The Late Cretaceous–early Paleogene tectonic evolution of the Iranian Plateau is not well understood in comparison to its well-studied late Paleogene–Neogene evolution. Exhumation, metamorphism, and changing sedi¬mentary environments are documented away from the plateau margin for this time interval, however the nature and mechanism of deformation in the interior of the Iranian Plateau remains controversial to the point that both compressional and extensional mechanisms are proposed. We use K-feldspar and mica ^(40)Ar/^(39)Ar thermochronology to determine the thermal evolution of metamorphic rocks exposed in northeastern Great Kavir Basin on the Iranian Plateau. Multi-domain diffusion modeling of K-feldspar and field relationships reveal a stage of rapid cooling via tectonic exhumation starting in the Late Cretaceous and lasting until the early Eocene. We attribute this to continental extension as being accommodated on detachment faults that exhumed the Shotor Kuh–Biarjmand metamorphic core complex. The metamorphic rocks of this core complex underlie a southeastward-younging structural-stratigraphic sequence that includes at its top Late Cretaceous (Campanian–Maastrichtian) carbonates. We interpret this sequence as a crustal section that was exhumed by a NW-dipping master detachment fault. Based on the locations of the syn-extensional detrital rocks we propose that this system accommodated ∼100 km of NW-SE–oriented extension. Our results indicate that extensional deformation started in the Iranian Plateau much earlier (Late Cretaceous) than previously thought (Eocene–Oligocene).


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http://dx.doi.org/10.1130/GES01423.1DOIArticle
https://pubs.geoscienceworld.org/geosphere/article-lookup?doi=10.1130/GES01423.1PublisherArticle
Additional Information:© 2017 Geological Society of America. Received 25 August 2016; Revision received 22 February 2017; Accepted 18 April 2017; First Published on June 20, 2017. This work was partially supported by Geological Society of America Graduate Student Research Grant awarded to the first author. Funding for analyses was provided by the New Mexico Geochronology Research Laboratory. We thank Amir Esna-Ashari for facilitating access to our samples in Iran. Jolante van Wijk, Shari Kelly, and William McIntosh are thanked for their helpful reviews of early drafts of this manuscript. The authors also thank Bernard Guest and two anonymous reviewers for thorough and constructive comments.
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Geological Society of AmericaUNSPECIFIED
New Mexico Geochronology Research LaboratoryUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20170620-161806951
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170620-161806951
Official Citation:Ahmadreza Malekpour-Alamdari, Gary Axen, Matthew Heizler, Jamshid Hassanzadeh; Large-magnitude continental extension in the northeastern Iranian Plateau: Insight from K-feldspar 40Ar/39Ar thermochronology from the Shotor Kuh–Biarjmand metamorphic core complex. Geosphere ; 13 (4): 1207–1233. doi: https://doi.org/10.1130/GES01423.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78391
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Jun 2017 00:09
Last Modified:03 Oct 2019 18:08

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