Three dimensional electrical structure of Southern Tibet across the northern part of Yadong-Gulu Rift.

Abstract:

As a young rift among the extensively spreading north-south trending Cenozoic structures in southern Tibet, Yadong-Gulu Rift (YGR) is characterized by varying geophysical parameters across it, especially the high conductive layers in the middle and lower crust which extend discontinuously in the east-west direction. Both ModEM and Wsinv3dmt three dimentional (3D) inversion codes are used to explore the characteristics of lithospheric deformation, lithosphere rheology and metallogenic mechanism in Southern Tibet. The main feature of the 3D electrical structure is that the high conductive bodies in the middle crust tend to converge deep beneath YGR. Based on the forward modeling of modified 3D models, a double Moho with the upper boundary at 60 km and lower boundary at 80 km is proved to exist in the lower crust. And the high conductive bodise in the middle and lower crust may result from magma underplating and upwelling of the deep asthenosphere material caused by plate convergence besides partial melting. In terms of the formation of YGR, it can be attributed to the rheology difference of lithosphere between the two sides of YGR. According to the 3D inversion result and other petrological studies, the effective viscosity of rocks beneath Southern Tibet is low enough to produce rheology. The east-west rheology difference is probably caused by the plate tearing of the obliquely subducted Indian Plate.