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Estimating the viscosity and Prandtl number of the Tso Morari crystalline gneiss dome, Indian western Himalaya

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Title Estimating the viscosity and Prandtl number of the Tso Morari crystalline gneiss dome, Indian western Himalaya
 
Creator MUKHERJEE, S
MULCHRONE, KF
 
Subject Viscosity
Prandtl number
Newtonian viscous fluid
Rheology
Tso Morari Dome
UHP terrain
Himalaya
ULTRAHIGH-PRESSURE METAMORPHISM
ECLOGITE RHEOLOGY
CONTINENTAL SUBDUCTION
NORTHWEST HIMALAYA
DEEP SUBDUCTION
NUMERICAL-SIMULATION
EXHUMATION HISTORY
GEODYNAMIC MODELS
UHP METAMORPHISM
HIGH-TEMPERATURE
 
Description The Tso Morari crystalline (TMC) gneiss dome in the Indian Himalaya extruded from a depth of 120 km through an inclined subduction channel of sub-elliptical cross-section at the leading edge of the Indian plate. The velocity profile of this gneiss dome is derived after (1) presuming its incompressible Newtonian rheology, (2) finding the "best fit" of the outcrop of the gneiss dome to an ellipse, (3) taking into account different lithologies to have existed at the top of the extruding gneiss body, (4) considering the extrusion to have been driven by the buoyant push of the denser mantle beneath the lighter gneiss, and (5) assigning a range of plausible densities for different litho-units. Fitting the known rates of extrusion-from a few centimetres up to about one-hundredth of a millimetre per year-from 53 Ma onwards of this gneiss dome to its velocity profile constrains its maximum possible viscosity to 7.5 x 10(22) Pa s. This magnitude is 10(2)-10(4) times higher than previous estimates for gneisses and granites. Alternative explanations of our data are the following: (1) There was a fall in extrusion rates of the TMC gneiss from 53 to < 30 Ma because of an increase in the estimated maximum viscosity from 6.2 x 10(20) to 7.5 x 10(22) Pa s, possibly indicating a fall in temperature and/or compositional change of the TMC gneiss. (2) Lower the extrusion rates, higher are the estimated viscosities. (3) The TMC gneiss was more viscous probably due to its eclogite content. (4) The estimated maximum viscosity is 10(2) times higher than that in collision zones and 10(2)-10(4) times than that in the Tibetan lower crust, but broadly conforms to that for the crustal channel, and average lithospheric and asthenospheric values. The high magnitude of maximum possible Prandtl number of 10(28) of the TMC gneiss might be related to isothermal decompression of the gneiss during its extrusion.
 
Publisher SPRINGER
 
Date 2014-10-15T15:13:54Z
2014-10-15T15:13:54Z
2012
 
Type Article
 
Identifier INTERNATIONAL JOURNAL OF EARTH SCIENCES, 101(7)1929-1947
1437-3254
1437-3262
http://dx.doi.org/10.1007/s00531-012-0758-3
http://dspace.library.iitb.ac.in/jspui/handle/100/15124
 
Language en