The evolution of the Xar Moron tectonic belt in the eastern Central Asian Orogenic Belt: Constraints from evidences of deformation and low-temperature thermochronology

It is controversial that when and where the eastern part of the Central Asian Orogenic Belt was closed. The regional geological survey results of the ophiolitic mélanges and surrounding assemblages in Linxi area in eastern part of the Central Asian Orogenic Belt show that the Xar Moron tectonic belt, represented by Xingshuwa ophiolitic mélange and Shuangjing schist, is a late Paleozoic accretionary wedge in which the typical block and matrix structures are developed. The accretionary wedge, covered by the Middle to Late Permian Kedehe conglomerate rocks, has experienced three stages of deformation:including the earliest deformation indicated by the EW-trending structures formed during the southward subduction stage, the northward thrusting deformation in which the Middle and Late Permian strata were involved, and the deformation in the collision stage. From the Late Permian to the Early Triassic, the ophiolitic mélanges and overlying Kedehe conglomerate rocks underwent strong regional dextral ductile shearing and strain partition. The Late Permian regional dextral ductile shearing zone developed on the southern margin of the Central Asian Orogenic Belt, indicating that the Central Asian Orogenic Belt had already entered the intracontinental stage by that time. The Shuangjing schist experienced deformations similar to the ophiolitic mélanges, and the lower part was metamorphosed and uplifted to the surface during the collision period. Combined with zircon and apatite low-temperature thermochronologyical date, it is conclude that the Shuangjing schist and the ophiolite mélanges have experienced NS-trending compression caused by the closure of the northern Mongol-Okhotsk Ocean in the Middle to Late Jurassic, and the regional extension occurred throughout East Asia during the Early Cretaceous and the short-term tectonic inversion occurred in the Late Cretaceous.