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
AuthorWorthington, James R.
Chapman, James B.
Stevens Goddard, Andrea
Brooks, Hanna L.
Lamadrid, Hector M.
Hacker, Bradley R.
AffiliationUniv Arizona, Dept Geosci
MetadataShow full item record
PublisherAMER GEOPHYSICAL UNION
CitationWorthington, 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 Syncollisional Gneiss-Dome Complex and Connection to Lithospheric Processes. Tectonics, 39, e2019TC005735. https://doi.org/10.1029/2019TC005735
RightsCopyright © 2019. American Geophysical Union. All Rights Reserved.
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AbstractNeogene, 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 x 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 degrees C from 16-4 Ma; tectonic cooling/exhumation rates (42 degrees C/Myr, 1.1 km/Myr) contrast with erosion-dominated rates in the hanging wall (2 degrees 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.
Note6 month embargo; published online: 15 January 2020
VersionFinal published version