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Structural complexity resulting from pervasive ductile deformation in the Karakoram Shear Zone, Ladakh, NW India
Author(s) -
McCarthy M. R.,
Weinberg R. F.
Publication year - 2010
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2008tc002354
Subject(s) - sinistral and dextral , geology , shear zone , transpression , mylonite , batholith , shear (geology) , greenschist , seismology , geochemistry , petrology , tectonics
The NW‐SE trending, ∼800 km long, dextral Karakoram Shear Zone bounds southwest Tibet. We investigate an area immediately NW of the Pangong Lake where midcrustal rocks sections of the shear zone are exposed. Here, the dominant shear zone is characterized by dextral mylonitic rocks sheared at amphibolite facies and partly retrogressed to greenschist facies. These rocks define a kilometric, SE plunging inclined‐to‐recumbent fold in the footwall of a north directed, oblique dextral thrust that exhumed anatectic rocks of the Pangong Range. Argon cooling ages reveal that the Pangong Range cooled from ∼700°C to 300°C between ∼18–15 and ∼10 Ma, contemporaneously with overthrusting. Toward the SE, closer to the Pangong Lake, this kilometric fold is rotated from its NW–SE trend to an E–W trend, and the sense of shear changes to sinistral, with a broadly north directed thrusting component. The documented structures contradict predictions of normal movement in this area derived from considerations of rigid block behavior of the crust and support the interpretation that the system records dextral transpression. Thrusting and exhumation of the deeper and hot rocks exposed in the Pangong Range, folding of the thrust footwall, and the development of a sinistral E–W trending shear zone are all compatible with transpression caused by a northward push by a rigid indenter such as the Ladakh Batholith.