Three-dimensional electrical structure of the Huya fault and adjacent areas of the eastern margin of the Tibetan Plateau and its geological significance

Abstract

In this study, we present new two- and three-dimensional resistivity models of the Huya fault region in the east margin of the Tibetan Plateau, imaged with magnetotelluric (MT) method. According to those models, a high-angle low-resistivity anomaly beneath the Huya fault is revealed, which is interpreted as a crustal thrust fault. The Minshan Uplift is imaged as a two-layered resistivity structure. The Bikou Block exhibits relatively uniform high-resistivity characteristics in our models, with its basement connected to a high-resistivity body beneath the Longmenshan fault belt. Thus, we infer that the Bikou Block belongs to the Yangtze Block. The Longmenshan fault belt exhibits strips of alternating high- and low-resistivity anomalies in the upper crust, with its middle and lower crust being highly resistive. The middle and lower crust of the western study region shows low resistivity, with its geometry changed greatly as it extends southeastward and upward. This is interpreted as an eastward channel of escaping material of the Tibetan Plateau. However, this channel is imaged to be blocked horizontally by the Bikou Block near the Huya fault, causing part of mid-to-lower crustal material to be upwelling, resulting in the Minshan Uplift. Another part of the low resistivity anomaly extended southeastward and was blocked by the lithospheric high-resistivity body beneath the Longmenshan fault belt, and then extended to the northeast and the southwest.