Magnetotelluric Imaging of the Central Himalayan Crust Away From Rift Zones

Imaging the crustal structure and state of the Himalayan Orogenic Belt (HOB) is of great significance for understanding crustal deformation and its tectonic response in the collision front of the Indian-Eurasian plates. To avoid the influence from the anomalies underneath the north-south trending rifts, a three-dimensional electrical resistivity model across the central HOB was obtained between the Dingjie-Shenzha and Yadong-Gulu rifts. No lower-crustal conductor was found in the southern Lhasa Terrane, and the lower crust with a moderate resistivity value of approximately 100 omega m is interpreted to be the residue of previous partial melting beneath the Gangdese porphyry copper deposits. The middle crust between the Main Himalayan Thrust and Southern Tibet Detachment System is electrically resistive to the north of the north Himalayan gneiss domes (NHGD) belt and conductive to the south. The middle crust in the northern Himalayas may have undergone partial melting and crystallization during southward migration and duplexing. There is a strong deep-shallow coupling relationship in the central HOB, where an increase in the underthrusting angle of the Indian crust has resulted in a southward turn of the NHGD belt. The Himalayan Orogenic Belt (HOB) is an ideal place to study the deep-shallow coupling relationship of the continental collision system. Magnetotelluric sounding (MT) is a powerful tool for detecting the internal structure and state of collision zones. However, most of the previous results have been overprinted by north-south trending rifts. Therefore, a high-resolution three-dimensional electrical resistivity model was obtained across the central HOB through an MT profile between the Dingjie-Shenzha and Yadong-Gulu rifts, combined with the latest MT result from the Sikkim region. The electrical resistivity model revealed that the lower crust of the southern Lhasa Terrane is characterized by a moderate resistivity value of approximately 100 omega m; this may have provided the magma source for the porphyry copper deposits in the eastern Gangdese metallogenic belt and the southward thermal migration in the northern Himalayas. The middle crust of the northern Himalayas is electrically discontinuous toward the south, mainly exhibiting high resistivity north of the north Himalayan gneiss domes (NHGD) belt. The middle crust of the northern Himalayas may have undergone partial melting and crystallization during southward uplift and migration. We found a strong coupling relationship between the surface NHGD belt and the underthrusting of the Indian crust. A three-dimensional electrical resistivity model was obtained across the central HOB between the Dingjie-Shenzha and Yadong-Gulu rifts A moderate resistivity value in the lower crust of the southern Lhasa Terrane may represent the residue of previous partial melting The middle crust in the northern Himalayas is electrically discontinuous