I) MT Studies:
Magnetotelluric exploration mainly measures the apparent resistivities at various frequencies. MT data collected during INDEPTH project detected unusually high electrical conductivity across most of the north to south middle and lower crust of the Tibetan plateau (Wei et al 2001). This anomaly was attributed to the widespread presence of partial melt and/or aqueous fluids within the Tibetan plateau. Constructed electrical conductivity models indicates depths of 15 to 20 km in southern Tibet and 30 to 40 km in northern Tibet for a high conductivity layer (figure 23).
Figure 23. Electrical conductivity model for northern Tibet. The bottom panel show the conductance to 100 km [Wei et al. 2001].
Possible alternatives to the partial melt / aqueous fluids are metallic ore deposits and carbon films but extraordinary thicknesses is needed to attain the observed anomaly. It is also very important to know that this method is not able to constrain the lower limit of the conductive layer. Therefore, the vertical extent of the anomaly seen in the profile show widespread geometry (figure 23). In addition, interpretation of partial melt / aqueous fluid does not agree with xenolith studies which indicates high temperature of heating under dry conditions (Hacker et al. 2000).
A) Tectonics & Geology B) Seismicity C) GPS D) Seismic profiles & Tomography
E) Gravity F) Anisotropy G) Paleomagnetism H) Geochemistry I) MT studies
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