Study on the resistivity anisotropy of the lithosphere in the Solonker suture zone and its adjacent areas

The central region of the Solonker Suture Zone (SSZ), along with its adjacent areas, underwent considerable tectonic activity, which included the closure of the Paleozoic Paleo-Asian Ocean, the closure of the Mesozoic Mongolian Okhotsk Ocean, and the subduction of the Pacific plates during the Mesozoic and Cenozoic eras. These processes have led to the development of intricate deep structures within the region. Prior research has indicated that the Solonker suture zone and its adjacent areas display electrical anisotropy. To explore this phenomenon in greater depth, we employed magnetotelluric data, encompassing both broadband and long-period measurements gathered between 2010 and 2012. The initial analysis of the data focused on dimensionality and induction vector, resulting in a preliminary conclusion indicating the presence of electrical anisotropy in the region under investigation. Following this, the mare2dem code, created by Kerry Key, was utilized to produce two-dimensional isotropic and anisotropic resistivity models through the joint inversion of magnetotelluric (MT) and dipole-dipole data. This subsequent analysis provided further evidence supporting the existence of resistivity anisotropy in the area. The inversion results indicate that the anisotropic structures within this region typically demonstrate elevated conductivity. Taking into account the thermal properties of the study area, it can be deduced that the identified anisotropy is likely a consequence of the melting of graphite minerals. This phenomenon is attributed to the deposition of black shale, and the characteristics of both the source and volume of this deposition indicate a multi-stage closure of the ancient Asian Ocean, progressing from west to east.