Seismic velocity structures and deep dynamic processes in the crust and mantle beneath the Tianshan Orogenic Belt

As a typical region of intracontinental orogeny, the Tianshan Orogenic Belt has consistently attracted significant scientific interest from geologists, both in China and internationally. The distribution of velocity anomalies beneath the Tianshan Orogenic Belt is of profound importance as it sheds light on the response of orogenic areas to activation mechanisms. In this study, crust-mantle velocity anomalies were investigated in different sections of the Tianshan Orogenic Belt, as well as the formation mechanisms of these anomalies and the dynamic evolution process of uplift and deformation. Different seismic methodologies were applied, including tomographic imaging, receiver function analysis, and GPS observations. The results of this systematic analysis indicate that regional velocity anomalous structures are closely correlated with the geological tectonic features and dynamic evolutionary processes in the Tianshan Orogenic Belt and its surrounding areas. Specifically, the characteristics of the high-velocity anomalous structures beneath the Tianshan Orogenic Belt, including the tilt direction, morphology, and location of these structures, are evidence of a unique intracontinental subduction mechanism. Furthermore, the presence of low-velocity anomalous structures in different regions of the belt indicates the existence of small mantle plumes or small-scale mantle convection caused by upwelling thermal material from the asthenosphere as well as partial melting within the crust due to magma underplating. These findings have significant implications for further understanding of the dynamic processes in the Tianshan region, including intracontinental subduction, crustal shortening deformation, lithospheric delamination, and the upwelling of asthenospheric materials. The results also serve as valuable reference data for further study of the seismic activity distribution in the Tianshan area.