HR: 14:00h
AN: T53D-02    [Abstracts]
TI: Magnetotelluric observations of crustal deformation and flow in Tibet
AU: * Unsworth, M
EM: unsworth@phys.UAlberta.ca
AF: University of Alberta, Department of Physics, Edmonton, AB T6G 2J1 Canada
AU: Bai, D
EM: dhbai@mail.igcas.ac.cn
AF: Chinese Academy of Sciences, Institute of Geology and Geophysics, Beijing, 100098 China
AU: Jones, A
EM: alan@cp.dias.ie
AF: Dublin Institute of Advanced Study, School of Cosmic Physics, Dublin, 2 Ireland
AU: Wei, W
EM: wwb@cugb.edu.cn
AF: China University of Geosciences, Department of Applied Geophysics, Beijing, 100083 China
AB: Geophysical data are a vital source of information regarding the processes at work in active orogens. For example, seismic reflection and magnetotelluric (MT) studies of the Tibetan-Himalayan orogen have revealed zones of partial melting that may delineate regions of rheological weakness. This includes the mid-crustal melt layer in southern Tibet that was imaged with both seismic reflection and MT data, and is associated with the south directed flow that has exhumed the High Himalyan leucogranites. In northern and eastern Tibet, crustal flow has been proposed to account for the observed topography and may be required to maintain a mass balance. A channel of enhanced electrical conductivity has been observed in the Tibetan crust on the INDEPTH data and also in new MT data collected in eastern Tibet. Could this feature represent one such channel of crustal flow? However, geophysical datasets must be carefully interpreted in a number of situations. Firstly, the absence of high conductivity does not exclude the possibility that deformation is occurring through other mechanisms such as creep. Secondly, other minor phases can produce a high electrical conductivity, notably electronic conduction in graphite, sulphides, iron oxides and ionic conduction in aqueous fluids. Finally, there are locations where high electrical conductivity is observed in the absence of a seismic anomalies. If carefully analyzed, and compared and contrasted with other geophysical and geoscientific data, each of these scenarios allows a broader understanding of orogenesis.
DE: 8102 Continental contractional orogenic belts
DE: 8159 Rheology--crust and lithosphere
DE: 7205 Continental crust (1242)
DE: 3630 Experimental mineralogy and petrology
DE: 3902 Creep and deformation
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting