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Geology and thermochronology of Tertiary Cordilleran-style metamorphic core complexes in the Saghand region of central Iran

Verdel, Charles and Wernicke, Brian P. and Ramezani, Jahandar and Hassanzadeh, Jamshid and Renne, Paul R. and Spell, Terry L. (2007) Geology and thermochronology of Tertiary Cordilleran-style metamorphic core complexes in the Saghand region of central Iran. Geological Society of America Bulletin, 119 (7-8). pp. 961-977. ISSN 0016-7606.

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An ~100-km-long north-south belt of metamorphic core complexes is localized along the boundary between the Yazd and Tabas tectonic blocks of the central Iranian micro-continent, between the towns of Saghand and Posht-e-Badam. Amphibolite facies mylonitic gneisses are structurally overlain by east-tilted supracrustal rocks including thick (>1 km), steeply dipping, nonmarine siliciclastic and volcanic strata. Near the detachment (the Neybaz-Chatak fault), the gneisses are generally overprinted by chlorite brecciation. Crosscutting relationships along with U-Pb zircon and ^(40)Ar/^(39)Ar age data indicate that migmatization, mylonitic deformation, volcanism, and sedimentation all occurred in the middle Eocene, between ca. 49 and 41 Ma. The westernmost portion of the Tabas block immediately east of the complexes is an east-tilted crustal section of Neoproterozoic–Cambrian crystalline rocks and metasedi-mentary strata >10 km thick. The ^(40)Ar/^(39)Ar biotite ages of 150–160 Ma from structurally deep parts of the section contrast with ages of 218–295 Ma from shallower parts, and suggest Late Jurassic tilting of the crustal section. These results define three events: (1) a Late Jurassic period of upper crustal cooling of the western Tabas block that corresponds to regional Jurassic–Cretaceous tectonism and erosion recorded by a strong angular unconformity below mid-Cretaceous strata throughout central Iran; (2) profound, approximately east-west middle Eocene crustal extension, plutonism, and volcanism (ca. 44–40 Ma); and (3) ~2–3 km of early Miocene (ca. 20 Ma) erosional exhumation of both core complex and Tabas block assemblages at uppermost crustal levels, resulting from significant north-south shortening. The discovery of these and other complexes within the mid-Tertiary magmatic arcs of Iran demonstrates that Cordilleran-style core complexes are an important tectonic element in all major segments of the Alpine-Himalayan orogenic system.

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Wernicke, Brian P.0000-0002-7659-8358
Additional Information:© 2007 Geological Society of America. Manuscript received 12 September 2006; Revised manuscript received 1 February 2007; Manuscript accepted 14 February 2007. We thank the University of Tehran Research Council for their support of this project and Ahmad Reza Malekpour for his efforts in the field. Ken Farley, Rebecca Flowers, and Lindsey Hedges provided assistance with the (U-Th)/He analyses. Bernard Guest and Kevin Mahan conducted informal reviews of an early version of the manuscript. Mahan also offered helpful advice in microstructural analysis. Comments from Mark Allen, David Foster, and Uwe Ring improved the manuscript. Financial support for this project was provided by the Caltech Tectonics Observatory and National Science Foundation grant EAR-0511054.
Group:Caltech Tectonics Observatory
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Caltech Tectonics ObservatoryUNSPECIFIED
Subject Keywords:metamorphic core complex; extensional; tectonics; thermochronology; Iran; Alpine-Himalayan; orogen; Arabia-Eurasia collision
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Caltech Tectonics Observatory65
Issue or Number:7-8
Record Number:CaltechAUTHORS:20101115-103409069
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20806
Deposited By: Tony Diaz
Deposited On:15 Nov 2010 23:54
Last Modified:03 Oct 2019 02:15

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