Abstract: The Central Asian orogenic belt (CAOB), which experienced ~800 Ma of subduction–accretion associated with the Paleo-Asian Ocean, represents one of the largest and most complex accretionary orogenic systems on Earth. It records key geological processes, including oceanic subduction, crustal accretion, and subsequent tectonic overprinting, thus provides a crucial window for investigating Phanerozoic continental evolution within the Paleo-Asian Ocean tectonic domain. The Solonker suture, located in the south-central segment of the CAOB, records the evolution and final closure of this ocean and is widely regarded as its terminal suture. However, the eastward extension of this suture and the subduction polarity of the Paleo-Asian Ocean in this region remain subjects of significant debate. In recent years, two deep seismic reflection profiles of large dynamite shots have been developed across the Solonker suture, extending the detection depth to the lithospheric mantle and successfully revealing the seismic structural characteristics of fossil subduction zones beneath the suture. This study synthesizes and contrasts the seismic structures imaged by these two profiles and integrates them with newly acquired geophysical datasets to characterize the lithosphere-scale deformation architecture of the study area. The combined geological and geophysical evidence demonstrates that the Paleo-Asian Ocean underwent divergent double subduction in the south-central CAOB, culminating in its final closure along the Solonker–Tuquan between the Hegenshan and Xar-Moron sutures, with its eastern extension reaching into the central Songliao basin.

Key words: Central Asian orogenic belt, Paleo-Asian Ocean, lithospheric structures, Solonker suture, fossil subduction zone