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Higher Himalayan Shear Zone, Sutlej section: structural geology and extrusion mechanism by various combinations of simple shear, pure shear and channel flow in shifting modes

DSpace at IIT Bombay

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Title Higher Himalayan Shear Zone, Sutlej section: structural geology and extrusion mechanism by various combinations of simple shear, pure shear and channel flow in shifting modes
 
Creator MUKHERJEE, S
KOYI, HA
 
Subject main central thrust
south tibetan detachment
inverted metamorphism example
nepal himalaya
ductile shear
collision tectonics
manaslu leukogranite
zanskar himalaya
western zanskar
everest massif
higher himalayan shear zone
extrusion
ductile shearing
channel flow
brittle shearing
detachment
 
Description The Higher Himalayan Shear Zone (HHSZ) in the Sutlej section reveals (1) top-to-SW ductile shearing, (2) top-to-NE ductile shearing in the upper- and the lower strands of the South Tibetan Detachment System (STDS(U), STDS(L)), and (3) top-to-SW brittle shearing corroborated by trapezoid-shaped minerals in micro-scale. In the proposed extrusion model of the HHSZ, the E(1)-phase during 25-19 Ma is marked by simple shearing of the upper sub-channel defined by the upper strand of the Main Central Thrust (MCT(U)) and the top of STDS(U) as the lower- and the upper boundaries, respectively. Subsequently, the E(2a)-pulse during 15-14 Ma was characterized by simple shear, pure shear, and channel flow of the entire HHSZ. Finally, the E(2b)-pulse during 14-12 Ma observed simple shearing and channel flow of the lower sub-channel defined by the lower strand of the Main Central Thrust (MCT(L)) and the top of the STDS(L) as the lower- and the upper boundaries, respectively. The model explains the constraints of thicknesses of the STDS(U) and the STDS(L) along with spatially variable extrusion rate and the inverted metamorphism of the HHSZ. The model predicts (1) shear strain after ductile extrusion to be maximum at the boundaries of the HHSZ, which crudely matches with the existing data. The other speculations that cannot be checked are (2) uniform shear strain from the MCT(U) to the top of the HHSZ in the E(1)-phase; (3) fastest rates of extrusion of the lower boundaries of the STDS(U) and the STDS(L) during the E(2a)- and E(2b)-pulses, respectively; and (4) variable thickness of the STDS(L) and rare absence of the STDS(U). Non-parabolic shear fabrics of the HHSZ possibly indicate heterogeneous strain. The top-to-SW brittle shearing around 12 Ma augmented the ductile extruded rocks to arrive a shallower depth. The brittle-ductile extension leading to boudinage possibly did not enhance the extrusion.
 
Publisher SPRINGER
 
Date 2011-08-29T13:49:20Z
2011-12-26T12:58:37Z
2011-12-27T05:48:51Z
2011-08-29T13:49:20Z
2011-12-26T12:58:37Z
2011-12-27T05:48:51Z
2010
 
Type Article
 
Identifier INTERNATIONAL JOURNAL OF EARTH SCIENCES, 99(6), 1267-1303
1437-3254
http://dx.doi.org/10.1007/s00531-009-0459-8
http://dspace.library.iitb.ac.in/xmlui/handle/10054/12100
http://hdl.handle.net/10054/12100
 
Language en