Electrical conductivity structure of the Qinghai-Tibet Plateau and its significance for the study of the lithosphere

Abstract: Three nearly N-S-trending magnetotelluric (MT) sounding profiles (Yadong-Xuegula, Dagzê-Bam Co, Nagqu-Golmud) were deployed across the Qinghai-Tibet Plateau to detect and study the electrical conductivity structure of the crust and upper mantle using the superwide band MT method. The main characters of the electrical conductivity structure along the three profiles are as follows: (1) in the segment south of Nagqu, the electrical layer is thin, and the low-resistivity bodies are mostly distributed discontinuously in the form of a string of beads and apparently dip north at 20°～ 30°; (2) in the segment between Nagqu and Yanshiping, the thickness of the electrical layer is increased, and the low- or high-resistivity bodies occur as subhorizontal thin sheets; (3) in the segment north of Yanshiping, the electrical layer is thicker, and the low-resistivity bodies occur as big lenses dipping south relatively continuously at ~40°; and(4) the features of the electrical layers in the three segments are markedly different and closely related to the regional tectonic setting and magmatic activity. These important electrical characters provide important geophysical evidence for studying the mechanism of India-Eurasia collision.