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Exhumation of the west-central Alborz Mountains, Iran, Caspian subsidence, and collision-related tectonics

Axen, Gary J. and Lam, Patrick S. and Grove, Marty and Stockli, Daniel F. and Hassanzadeh, Jamshid (2001) Exhumation of the west-central Alborz Mountains, Iran, Caspian subsidence, and collision-related tectonics. Geology, 29 (6). pp. 559-562. ISSN 0091-7613. doi:10.1130/0091-7613(2001)029<0559:EOTWCA>2.0.CO;2.

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Crystallization and thermal histories of two plutons in the west-central Alborz (also Elburz, Elburs) Mountains, northern Iran, are combined with crosscutting relations and kinematic data from nearby faults to determine the Cenozoic tectonic evolution of this segment of the youthful Euro-Arabian collision zone. U/Pb, ^(40)Ar/^(39)Ar, and (U-Th)/He data were obtained from zircon, biotite, K-feldspar, and apatite. The Akapol pluton intruded at 56 ± 2 Ma, cooled to ∼150 °C by ca. 40 Ma, and stayed near that temperature until at least 25 Ma. The nearby Alam Kuh granite intruded at 6.8 ± 0.1 Ma and cooled rapidly to ∼70 °C by ca. 6 Ma. These results imply tectonic stability of the west-central Alborz from late Eocene to late Miocene time, consistent with Miocene sedimentation patterns in central Iran. Elevation-correlated (U- Th)/He ages from the Akapol suite indicate 0.7 km/m.y. exhumation between 6 and 4 Ma, and imply ∼10 km of Alborz uplift that was nearly synchronous with rapid south Caspian subsidence, suggesting a causal relation. Uplift, south Caspian subsidence and subsequent folding, reversal of Alborz strike-slip (from dextral to sinistral) and(?) eastward extrusion of central Iran, coarse Zagros molasse deposition, Dead Sea transform reorganization, Red Sea oceanic spreading, and(?) North and East Anatolian fault slip all apparently began ca. 5 ± 2 Ma, suggesting a widespread tectonic event that we infer was a response to buoyant Arabian lithosphere choking the Neo-Tethyan subduction zone.

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Additional Information:© 2001 Geological Society of America. Manuscript received November 20, 2000; Revised manuscript received February 23, 2001; Manuscript accepted March 6, 2001. We thank M. Mashaiekhi, E. Mashaiekhi, A. Sharifi, and B. Bashukooh for valuable field assistance, H. Beshavarpour for collecting sample 19-31-1, and C.D. Coath for help with ion microprobe work. This study was supported by the National Science Foundation (grant EAR-9902932 to Axen), the UCLA Council on Research (Axen), the University of Tehran Research Council (grant 651/1/328 to Hassanzadeh), the Department of Energy (grant DE-FG-03- 89ER14049 to T.M. Harrison), a Caltech postdoctoral fellowship (Stockli), and a Packard Foundation fellowship (K.A. Farley).
Funding AgencyGrant Number
UCLA Council on ResearchUNSPECIFIED
University of Tehran Research Council651/1/328
Department of Energy (DOE)DE-FG-03-89ER14049
Caltech Postdoctoral FellowshipUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:Iran; geochronology; collision; tectonics; exhumation; Caspian
Issue or Number:6
Record Number:CaltechAUTHORS:20130820-131207518
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40740
Deposited By: Tony Diaz
Deposited On:20 Aug 2013 22:50
Last Modified:10 Nov 2021 00:08

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