A review of geophysical studies on the Mongolian Plateau

Abstract

The Mongolian Plateau in Central Asia is an intracontinental tectonic system far from active plate boundaries. Despite its distance from these boundaries, the plateau is characterized by intense crustal deformation accompanied by voluminous Cenozoic volcanism and active modern seismicity. However, the intraplate deformation mechanism has long been debated owing to the scarcity of observations and contradictions between different results. In recent years, growing geophysical studies have been conducted on the Mongolian Plateau, providing constraints on its lithospheric structure and dynamics. Here, we review the geophysical research on the Mongolian Plateau over the last decade, including seismological, geodetic, gravity, magnetotelluric, and geodynamic aspects. This review aims to (a) describe crustal and mantle structures based on multiscale seismic images; (b) describe deformation patterns based on seismic anisotropy, focal mechanisms, and global positioning system (GPS) observations; and (c) discuss the mechanisms behind intraplate deformation, volcanism, and seismic activity across the Mongolian Plateau. Seismic images show that the crustal structure of the plateau has significant east-west differences. Several blocks in the western Mongolian Plateau have thick crusts, including the Altai Mountains, Hovsgol Rift, and Hangay Dome. The lithospheric deformation across the Mongolian Plateau has strong lateral variation, with NE-SW shortening in the Altai Mountains and W-E or NW-SE shear deformation in the Hangay Dome region and the eastern part. The varied deformation may result from the superposition of multiple mechanisms, including far-field stress in the Altai Mountains, mantle upwelling, and mantle flow in the Hangay Dome region. However, it is difficult to identify the geodynamics of the formation of the entire Mongolian Plateau because the deformation is too complicated, and the present models are not sufficient and are always partial. Overall, this review encompasses recent advances in seismic observations of the Mongolian Plateau, illuminates the heterogeneities in the crust and mantle structure and deformation of the plateau, and discusses the mechanisms behind the deformation, magmatism, and seismicity.