Crustal rheology of the Himalaya and Southern Tibet inferred from magnetotelluric data
Unsworth, M.J., A.G. Jones, W. Wei, G. Marquis, S. Gokarn, J.E. Spratt, and the INDEPTH-MT team
The Cenozoic collision between the Indian and Asian continents
formed the Tibetan plateau, beginning about 70 million years ago.
Since this time, at least 1,400km of convergence has been accommodated1
by a combination of underthrusting of Indian2 and
Asian lithosphere, crustal shortening3, horizontal extrusion4 and
lithospheric delamination5. Rocks exposed in the Himalaya show
evidence of crustal melting1,6 and are thought to have been
exhumed by rapid erosion and climatically forced crustal flow7,8.
Magnetotelluric data can be used to image subsurface electrical
resistivity, a parameter sensitive to the presence of interconnected
fluids in the host rock matrix, even at low volume fractions. Here
we present magnetotelluric data from the Tibetan–Himalayan
orogen from 778E to 92 E, which show that low resistivity,
interpreted as a partially molten layer, is present along at least
1,000 km of the southern margin of the Tibetan plateau.
The inferred low viscosity of this layer is consistent with
the development of climatically forced crustal flow in Southern
Nature, 438, 78-81, doi: 10.1038/nature04154, 2005.
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Alan G Jones / 21 April 2006 /