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Alichur Dome, South Pamir, Western India-Asia Collisional Zone: Detailing the Neogene Shakhdara-Alichur Syn-collisional Gneiss-Dome Complex and Connection to Lithospheric Processes

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. 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.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2019tc005735DOIArticle
https://osf.io/u6zha/?view_only=abe312f95192412584669da2f80e92c3Related ItemData
ORCID:
AuthorORCID
Worthington, James R.0000-0002-1442-8265
Ratschbacher, Lothar0000-0001-9960-2084
Stübner, Konstanze0000-0001-7473-9033
Khan, Jahanzeb0000-0002-3059-3228
Malz, Nicole0000-0003-3647-7196
Kapp, Paul0000-0002-7173-9908
Chapman, James B.0000-0002-1145-4687
Goddard, Andrea Stevens0000-0001-9405-7953
Brooks, Hanna L.0000-0003-1153-2179
Lamadrid, Hector M.0000-0002-0903-7382
Rutte, Daniel0000-0002-5121-7969
Hacker, Bradley R.0000-0003-2732-1712
Gadoev, Mustafo0000-0002-8157-393X
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.
Funders:
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)PAK 443
Bundesministerium für Bildung und Forschung (BMBF)03G0809
NSFEAR-1419748
ExxonMobilUNSPECIFIED
Geological Society of AmericaUNSPECIFIED
American Association of Petroleum GeologistsUNSPECIFIED
University of ArizonaUNSPECIFIED
Conoco PhilipsUNSPECIFIED
NSFEAR‐1338583
Fulbright FoundationUNSPECIFIED
Subject Keywords:gneiss domes; thermochronology; geochronology; continental collision; Pamir; structural geology
Issue or Number:1
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:03 Aug 2020 19:00

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