On the Origin of Crustal High Conductivity Zone in the Western Tibet plateau

The high conductivity zones (HCZ) are widely observed in the mid-to-lower crust of Tibet plateau by Magnetotellurics (MT) studies . They are commonly considered as the result of partial melting, with good correlation with low velocity zones. The HCZs are often arributed to some crustal (channel) flow, which may contribute to the regional tectonic evolutions, such as the significant shortening and thickening of the Plateau crust.

Here, we present a new 3-D resistivity model derived from SINOPROBE MT data collected from 80°-81°E in the Western Tibetan Plateau. Our model images isolated high conductivity zone in Lhasa block and Qiangtang Block. After estimating the content of HCZ, we believe the rheology may be different in these two blocks, in which the estimated melt fraction is not as high as previously reported. The Bankong-Nujiang Suture Zone separates the HCZs located in Lhasa and Qiangtang blocks, which may lead to the different movement direction of the crustal material. Moreover, a ~15km high resistivity layer is revealed beneath the Karakoram fault, which may imply that the east end of fault is not a lithospheric scale structure as previously discussed. This indicates that the role of the fault might change in the different geologic period.