Mechanism for the Uplift of Gongga Shan in the Southeastern Tibetan Plateau Constrained by 3D Magnetotelluric Data

Gongga Shan (GGS) is the highest mountain on the eastern margin of the Tibetan Plateau. However, the mechanism for the uplift of Gongga Shan is still unclear due to a lack of detailed geophysical studies. Inversion of an array of magnetotelluric data at 120 sites produced a 3D resistivity model that revealed that the GGS massif is characterized by a high resistivity upper crust underlain by a westward dipping resistor at middle crustal depths that is interpreted as the underthrust Yangtze Craton (YC). A thin conductive layer is sandwiched between these two zones of high resistivity. This resistivity model is inconsistent with previously published geodynamic models. Based on the new magnetotelluric results, we propose that the uplift of Gongga Shan occurs primarily by underthrusting of the YC. Additional uplift may be due to transpression on a restraining bend of the oblique-slip Xianshuihe faults.