Lithospheric electrical structure of western Qaidam Basin

The Qaidam Basin is rich in oil, gas, and mineral resources. Its origin and evolutionary process, composition, and deep structural characteristics play a crucial role in geological research on the Qinghai−Tibetan Plateau. Considering that magentotelluric sounding as one of the vital methods to study the electrical structure of the lithosphere, it can provide significant support for basin dynamics, resource exploration and deposit genesis research. To better analyze the tectonic significance of the key electrical layers in the lithosphere of the Qaidam Basin, we conducted a (ultra−) broadband magnetotelluric sounding line about 255 km long from the Youquanzi to the Huahaizi in the western Qaidam Basin, which obtained a 2D profile, and including the combination with regional geological, the existing geochemical and geophysical research results. In the western Qaidam Basin, two Cenozoic electrical layers with different deformation strength developed in the upper and lower strata. The upper electrical layers with weak deformation contains a set of ultra−low resistivity layers lower than 2 Ω·m, which corresponds to the high−quality brine layer in the deep basin, indicating a good prospect of deep brine prospecting. But the deformation of the lower electrical layer is relatively strong, and a set of growing electrical layer can be seen at the bottom. We considered that the existence of the main Qaidam detachment fault in the deep part controlled the Cenozoic sedimentary and tectonic deformation of the basin at the beginning of the Cenozoic. There are significant differences in the deep electrical structure of the research area, with a high and low undulating electrical Moho surface located about 50 kilometers deep. The deep parts of Qaidam Basin and Suganhu Basin are dominated by medium−low resistance bodies. The Saishiteng Mountain area is rooted with high resistivity body, while the middle and lower crust of the Youquanzi alkali mountain area is a set of low resistance bodies. There may be an upwelling of asthenosphere material in the deep of the Kunteyi area.