Seismo-tectonics and magma chambers revealed by the 3D resistivity model in western Yunnan

Abstract

Based on broadband magnetotelluric (MT) array data, we have obtained the three-dimensional (3-D) electrical resistivity model in western Yunnan, the southeastern Tibetan Plateau where the Quaternary intraplate Tengchong volcanism and seismic activities occur. Our MT model clearly reveals three conductive bodies in the depth ranges of 10–30 km in the Tengchong volcano area, which we interpret as three middle-lower crustal magma chambers associated with the Tengchong volcanism. Seismogenic faults in the Gaoligong Shear Zone (GLGSZ) are characterized by subvertical conductive zones bounded by resistive upper crustal layer on both sides. Earthquakes of moderate magnitudes near the GLGSZ have all occurred within the conductive fault zones at the bottom of the upper resistive crust. Our model also suggests a bifurcation of the crustal flow in western Yunnan, with a southwestern branch running into the Tengchong Block north of the Dayingjiang Fault and a southeastern branch flowing into the Baoshan Block. The current study provides evidence from electrical resistivity structure for the middle-lower crustal magma chambers in the Tengchong volcano area and detailed 3-D electrical structure of crustal channel flow in this active tectonic region.