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Mafic and pelitic xenoliths in the Kinnaur Kailash Granite, Baspa river valley, NW Himalaya: Evidence of pre-Himalayan granulite metamorphism followed by cooling event

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Title Mafic and pelitic xenoliths in the Kinnaur Kailash Granite, Baspa river valley, NW Himalaya: Evidence of pre-Himalayan granulite metamorphism followed by cooling event
 
Creator THAKUR, SS
PATEL, SC
 
Subject Granulite
Himalaya
Metamorphism
Corona texture
Kinnaur Kailash Granite
CONSISTENT THERMODYNAMIC DATA
INDIAN PLATE
ISOTOPIC CONSTRAINTS
ZIRCON AGES
HISTORY
ROCKS
GEOTHERMOMETER
ORTHOPYROXENE
SEDIMENTATION
GEOCHRONOLOGY
 
Description Mafic and pelitic xenoliths occurring within the early Palaeozoic Kinnaur Kailash Granite (KKG) in the Baspa river valley, NW Himalaya record pre-Himalayan regional metamorphism at a range of pressure (P)-temperature (T) conditions that span amphibolite to granulite fades. The key evidence of granulite metamorphism is a xenolith of two-pyroxene mafic granulite in which orthopyroxene occurs as both discrete grains and microscopic needles exsolved parallel to prismatic cleavage of the clinopyroxene host. The rock records an average peak metamorphic temperature of 840 degrees C. Garnetiferous mafic xenoliths display coronae of garnet around plagioclase and clinopyroxene, and of sphene around ilmenite. These coronae were developed by near-isobaric cooling after peak metamorphism at 730 degrees C and 8 kbar. Pelitic xenoliths have the assemblage biotite-plagioclase-quartz +/- garnet +/- K-feldspar +/- muscovite, and record P-T ranges of 7.0-9.0 kbar and 500-700 degrees C which indicate lower to middle amphibolite facies metamorphism of these rocks. Quartz, feldspar and mica in the pelitic xenoliths commonly show optical evidences of crystalloplastic deformation which indicate that the rocks were sheared before being engulfed as xenoliths in the KKG. The findings of this study imply that the present day metamorphic assemblages and shear fabrics in HHCS rocks need not be attributed solely to the Himalayan orogeny. (c) 2012 Elsevier Ltd. All rights reserved.
 
Publisher PERGAMON-ELSEVIER SCIENCE LTD
 
Date 2014-10-14T17:06:48Z
2014-10-14T17:06:48Z
2012
 
Type Article
 
Identifier JOURNAL OF ASIAN EARTH SCIENCES, 56105-117
http://dx.doi.org/10.1016/j.jseaes.2012.04.024
http://dspace.library.iitb.ac.in/jspui/handle/100/14526
 
Language en