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Channel flow extrusion model to constrain dynamic viscosity and Prandtl number of the Higher Himalayan Shear Zone

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Title Channel flow extrusion model to constrain dynamic viscosity and Prandtl number of the Higher Himalayan Shear Zone
 
Creator MUKHERJEE, S
 
Subject Channel flow
Shear zone
Viscosity
Prandtl number
Higher Himalaya
Higher Himalayan Shear Zone
Extrusion
MAIN CENTRAL THRUST
SOUTH TIBETAN DETACHMENT
ULTRAHIGH-PRESSURE METAMORPHISM
CONTINENTAL COLLISION ZONES
EASTERN NEPAL HIMALAYA
DUCTILE EXTRUSION
WESTERN HIMALAYA
TECTONIC EVOLUTION
BHUTAN HIMALAYA
INVERTED METAMORPHISM
 
Description Constraining magnitudes of mechanical and thermo-mechanical parameters of rocks and shear zones are the important goals in structural geology and tectonics (Talbot in J Struct Geol 21:949-957, 1999). Such parameters aid dynamic scaling of analogue tectonic models (Ramberg in Gravity, deformation and the Earth's crust in theory, experiments and geological applications, 2nd edn. Academic Press, London, 1981), which are useful to unravel tectonics in further details (Schultz-Ela and Walsh in J Struct Geol 24:247-275, 2002). The channel flow extrusion of the Higher Himalayan Shear Zone (HHSZ, = Higher Himalaya) can be explained by a top-to-S/SW simple shear (i.e. the D-2 deformation) in combination with a pressure gradient induced flow against gravity. Presuming its Newtonian incompressible rheology with parallel inclined boundaries, the viscosity (mu) of this shear zone along a part of the Himalayan chain through India, Nepal and Bhutan is estimated to vary widely between similar to 10(16) and 10(23) Pa s, and its Prandtl number (P (r) ) within similar to 10(21)-10(28). The estimates utilized ranges of known thickness (6-58 km) of the HHSZ, that of its top subzone of ductile shear of normal shear sense (STDSU: 0.35-9.4 km), total rate of slip of its two boundaries (0.7-131 mm year(-1)), pressure gradient (0.02-6 kb km(-1)), density (2.2-3.1 g cm(-3)) and thermal diffusivity (0.5 x 10(-6)-2.1 x 10(-6) m s(-2)) along the orogenic trend. Considering most of the parameters specifically for the Sutlej section (India), the calculated viscosity (mu) and the Prandtl number (P (r) ) of the HHSZ are deduced to be mu: similar to 10(17)-10(23) Pa s and P (r) similar to 10(22)-10(28). The upper limits of the estimated viscosity ranges are broadly in conformity with a strong Tibetan mid-crust from where a part of the HHSZ rocks extruded. On the other hand, their complete ranges match with those for its constituent main rock types and partly with those for the superstructure and the infrastructure. The estimated mechanical and thermo-mechanical parameters of the HHSZ will help to build dynamically scaled analogue models for the Himalayan deformation of the D-2-phase.
 
Publisher SPRINGER
 
Date 2014-10-15T15:15:24Z
2014-10-15T15:15:24Z
2013
 
Type Article
 
Identifier INTERNATIONAL JOURNAL OF EARTH SCIENCES, 102(7)1811-1835
1437-3254
1437-3262
http://dx.doi.org/10.1007/s00531-012-0806-z
http://dspace.library.iitb.ac.in/jspui/handle/100/15127
 
Language en