New Seismic Evidence for Continental Collision During the Assembly of the Central Asian Orogenic Belt

Abstract

Abstract The Central Asian Orogenic Belt (CAOB) was formed during the termination of the Paleo‐Asian Ocean in the Paleozoic. However, the mechanism and process of the Paleo‐Asian Ocean closure and CAOB formation remain controversial. This study presents a seismic image from the northern North China Craton to southern Mongolia derived from P and S receiver function analyses of the teleseismic records from a dense array. Our observations reveal a thicker lithosphere in the southern CAOB than in the Bohai Bay basin, which suggests that this Paleozoic orogen was less affected by the lithosphere reactivation in the eastern North China Craton during the Late Mesozoic. The imaged lithosphere‐asthenosphere boundary of the southern CAOB deepens southward and reaches a greatest depth of approximately 130 km beneath the Xilinhot fault, the northern boundary of the Solonker suture zone. The Moho displays a local uplift of approximately 5 km beneath the Linxi fault, the southern boundary of the Solonker suture zone. These features imply that the Solonker suture zone is the most plausible site of the lithosphere collision between the opposing continental margins. Additionally, a southward dipping intracrustal interface, whose depth extends from ~16 km beneath the Baolidao belt to ~20 km beneath the Linxi fault, is interpreted to be associated with the subduction of the Paleo‐Asian Oceanic slab. Additionally, the absence of lithosphere‐asthenosphere boundary phases beneath the Bainaimiao arc is inferred to be caused by the upwelling of hot mantle material after assembly of the CAOB.