Worthington, James R. and Ratschbacher, Lothar and Stübner, Konstanze and Khan, Jahanzeb and Malz, Nicole and Schneider, Susanne and Kapp, Paul and Chapman, James B. and Goddard, Andrea Stevens and Brooks, Hanna L. and Lamadrid, Hector M. and Steele‐MacInnis, Matthew and Rutte, Daniel and Jonckheere, Raymond and Pfänder, Jörg and Hacker, Bradley R. and Oimahmadov, Ilhomjon and Gadoev, Mustafo (2020) Alichur Dome, South Pamir, Western India-Asia Collisional Zone: Detailing the Neogene Shakhdara-Alichur Syn-collisional Gneiss-Dome Complex and Connection to Lithospheric Processes. Tectonics, 39 (1). Art. No. e2019TC005735. ISSN 0278-7407. doi:10.1029/2019tc005735. https://resolver.caltech.edu/CaltechAUTHORS:20200521-081615433
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Abstract
Neogene, syn‐collisional extensional exhumation of Asian lower–middle crust produced the Shakhdara–Alichur gneiss‐dome complex in the South Pamir. The <1 km‐thick, mylonitic–brittle, top‐NNE, normal‐sense Alichur shear zone (ASZ) bounds the 125 × 25 km Alichur dome to the north. The Shakhdara dome is bounded by the <4 km‐thick, mylonitic–brittle, top‐SSE South Pamir normal‐sense shear zone (SPSZ) to the south, and the dextral Gunt wrench zone to its north. The Alichur dome comprises Cretaceous granitoids/gneisses cut by early Miocene leucogranites; its hanging wall contains non/weakly metamorphosed rocks. The 22–17 Ma Alichur‐dome‐injection‐complex leucogranites transition from foliation‐parallel, centimeter‐ to meter‐thick sheets within the ASZ into discordant intrusions that may comprise half the volume of the dome core. Secondary fluid inclusions in mylonites and mylonitization‐temperature constraints suggest Alichur‐dome exhumation from 10–15 km depth. Thermochronologic dates bracket footwall cooling between ~410–130 °C from ~16–4 Ma; tectonic cooling/exhumation rates (~42 °C/Myr, ~1.1 km/Myr) contrast with erosion‐dominated rates in the hanging wall (~2 °C/Myr, <0.1 km/Myr). Dome‐scale boudinage, oblique divergence of the ASZ and SPSZ hanging walls, and dextral wrenching reflect minor approximately E–W material flow out of the orogen. We attribute broadly southward younging extensional exhumation across the central South Pamir between ~20–4 Ma to: (i) Mostly northward, foreland‐directed flow of hot crust into a cold foreland during the growth of the Pamir orocline; and (ii) Contrasting effects of basal shear related to underthrusting Indian lithosphere, enhancing extension in the underthrust South Pamir and inhibiting extension in the non‐underthrust Central Pamir.
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Additional Information: | © 2019 American Geophysical Union. Received 26 JUN 2019; Accepted 9 NOV 2019; Accepted article online 14 NOV 2019. Funded by DFG bundle TIPAGE (PAK 443); BMBF bundle CAME project TIPTIMON (Support Code 03G0809); NSF Grant EAR‐1419748; ExxonMobil; Geological Society of America; American Association of Petroleum Geologists; University of Arizona Coney fund; and Conoco Philips scholarship. The Arizona Laserchron Center was funded by NSF Instrumentation & Facilities Grant EAR‐1338583. A Fulbright Fellowship enabled J. W.'s. research at TU Bergakademie Freiberg. Reviews by A. Robinson and an anonymous reviewer and editorial handling by M. Jolivet and M.E. Rusmore improved this manuscript. We are grateful to the following individuals for providing analytical assistance: B. Sperner (Argonlab Freiberg); M. Hofmann and U. Linnemann (Senckenberg Labs); M. Pecha, N. Geisler, K. Plange, M. Pepper, and C. White (Arizona Laserchron Center); A. R. C. Kylander‐Clark (UCSB LASS Lab); U. Chowdhury (Arizona Radiogenic Helium Dating Lab); and Z. Zajacz (University of Toronto Fluid Inclusion Lab). Discussions with the GFZ Potsdam Pamir group (in particular S‐K. Kufner and B. Schurr), V. Minaev, B. Carrapa, P. DeCelles, M. Ducea, P. Reiners, K. Murray, S. Thompson, G. Gehrels, G. Davis, and J.‐P. Avouac improved this work. Our new data are available in Tables S1–S9 and Data Sets S1–S4 of the Supporting Information and at the Open Science Framework (https://osf.io/u6zha/?view_only=abe312f95192412584669da2f80e92c3). All cited data are available in referenced publications. | ||||||||||||||||||||||||||||
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Subject Keywords: | gneiss domes; thermochronology; geochronology; continental collision; Pamir; structural geology | ||||||||||||||||||||||||||||
Issue or Number: | 1 | ||||||||||||||||||||||||||||
DOI: | 10.1029/2019tc005735 | ||||||||||||||||||||||||||||
Record Number: | CaltechAUTHORS:20200521-081615433 | ||||||||||||||||||||||||||||
Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20200521-081615433 | ||||||||||||||||||||||||||||
Official Citation: | Worthington, J. R., Ratschbacher, L., Stübner, K., Khan, J., Malz, N., Schneider, S., et al. ( 2020). The Alichur Dome, South Pamir, Western India–Asia Collisional Zone: Detailing the Neogene Shakhdara–Alichur Syn‐collisional Gneiss‐Dome Complex and Connection to Lithospheric Processes. Tectonics, 39, e2019TC005735. https://doi.org/10.1029/2019TC005735 | ||||||||||||||||||||||||||||
Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||||||||||||||||||
ID Code: | 103374 | ||||||||||||||||||||||||||||
Collection: | CaltechAUTHORS | ||||||||||||||||||||||||||||
Deposited By: | Tony Diaz | ||||||||||||||||||||||||||||
Deposited On: | 21 May 2020 15:54 | ||||||||||||||||||||||||||||
Last Modified: | 16 Nov 2021 18:20 |
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