The deep electrical structure of Motuo fault zone in Beibeng area
Wang Gang
Fang Hui
Pei Fagen
Xiao Du
Zhang Xiaobo
Zhang Yaoyang
Peng Yan
Bai Dawei
Qiao Hanqing
Zhang Xiang
Chang Xiaopeng
Ge Xinwang
Ye Liushuai
Abstract：To elucidate the contact relationship between Indian and Eurasian plates along the Yarlung-Zangbo suture zone(IYS)and associated geodynamic processes,we acquired a high-resolution magnetotelluric(MT)pro-file extending 20 km across the Motuo fault zone near Beibeng Township,Motuo County,eastern Xizang.This NW-SE oriented transect employed 30 MT stations with approximately 300-m spacing,covering frequency bands of 10000-0.0001 Hz to resolve crustal structure down to 30 km depth.Key findings from the electrical resistivity model reveal:(1)At shallow crustal levels(<5 km depth),the Motuo fault system exhibits a negative flower struc-ture characterized by downward-converging conductive shear zones,diagnostic of dominant strike-slip deforma-tion.(2)Preservation of Indian slab subduction traces beneath the Lhasa Block along the IYS,with possible deve-lopment of a pop-up structure in the Indian upper crust near the eastern Himalayan syntaxis.(3)The resistive Lhasa Terrane upper crust is～20 km thick-33％thinner than the 30-km average in southern Xizang.This disparity im-plies either:(ⅰ)incomplete syn-collisional crustal shortening due to strain partitioning into strike-slip faults,or(ⅱ)absence of crustal growth episodes that thickened the Lhasa Terrane.(4)A mid-crustal conductor at 15-30 km depth aligns with the suture zone.Its upward-flaring geometry indicates southward migration of melts from the Lhasa lower crust,which is facilitated by transpressional uplift along the IYS.These results demonstrate that the Motuo fault system operates as a crustal-scale transfer zone,where strike-slip kinematics preserve early collisional features while enabling melt migration through reactivated suture structures.The integrated model provides new constraints on strain accommodation mechanisms during continental indentation.
Keywords：Yarlung-Zangbo suture zoneMotuo fault zonemagnetotelluricstructural framework
Publication Date：2025-11-30
Online Publishing Date：2025-09-12(First online date of this platform, not the publication date of the document)
Pages：11( 699-709 )