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Tectonic Implications and Morphology of Trapezoidal Mica Grains from the Sutlej Section of the Higher Himalayan Shear Zone, Indian Himalaya

DSpace at IIT Bombay

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Title Tectonic Implications and Morphology of Trapezoidal Mica Grains from the Sutlej Section of the Higher Himalayan Shear Zone, Indian Himalaya
 
Creator MUKHERJEE, S
 
Subject INVERTED METAMORPHISM
EXTRUSION
ROCKS
FLOW
 
Description Microscopic trapezoidal micas are reported from the Sutlej section of the Higher Himalayan Shear Zone, India, and are attributed to an up-dip top-to-southwest sense of brittle shear along C planes of preexisting ductile shear dipping northeast. The longest margins of these trapezoids dip northeast and are oblique to either the C planes or their enveloping planes. Intragrain slips along cleavages aided their thrusting, while the surrounding competent quartzofeldspathic minerals resisted it. The cleavages of the trapezoids are parallel to their longest margins. These cleavages, the longest margins, the overall asymmetry of trapezoid aggregates, and the trails emanating from their corners are reliable indicators of brittle shear sense. Trails broken from the corners of developing trapezoids define both the P and the Y shear planes. Subcircular stacks and triangular mineral grains are also possible variations of trapezoids. Some of the trapezoidal micas were products of ductile-brittle deformation. Variable intensities of dynamic recrystallization around the trapezoid margins indicate the rock did not strain-harden uniformly. The nongenetic interlinked morphological parameters of the trapezoid aspect ratio, internal angles, and local orientation vary widely and partially define the orientation and the geometry of the trapezoids. Further studies of the three-dimensional shapes and genesis of trapezoidal minerals are planned.
 
Publisher UNIV CHICAGO PRESS
 
Date 2014-10-15T15:16:54Z
2014-10-15T15:16:54Z
2012
 
Type Article
 
Identifier JOURNAL OF GEOLOGY, 120(5)575-590
http://dx.doi.org/10.1086/666744
http://dspace.library.iitb.ac.in/jspui/handle/100/15130
 
Language en