Tectonic evolution of the Beishan orogen in central Asia: Subduction, accretion, and continent-continent collision during the closure of the Paleo-Asian Ocean

The Beishan orogen is part of the Neo-proterozoic to early Mesozoic Central Asian Orogenic System in central Asia that exposes ophiolitic complexes, passive-margin strata, arc assemblages, and Precambrian base-ment rocks. To better constrain the tectonic evolution of the Beishan orogen, we con-ducted field mapping, U-Pb zircon dating, whole-rock geochemical analysis, and Sr-Nd isotopic analysis. The new results, when interpreted in the context of the known geo-logical setting, show that the Beishan region had experienced five phases of arc magma-tism at ca. 1450-1395 Ma, ca. 1071-867 Ma, ca. 542-395 Ma, ca. 468-212 Ma, and ca. 307-212 Ma. In order to explain the geologi-cal, geochemical, and geochronological data from the Beishan region, we present a tec-tonic model that involves the following five phases of deformation: (1) Proterozoic rifting that separated the North Beishan block from the Greater North China craton that led to the opening of the Beishan Ocean, (2) early Paleozoic north-dipping subduction (ca. 530- 430 Ma) of the Beishan oceanic plate associ-ated with back-arc extension followed by col-lision between the North and South Beishan microcontinental blocks, (3) northward slab rollback of the south-dipping subducting Paleo-Asian oceanic plate at ca. 450-440 Ma along the northern margin of the North Beishan block that led to the formation of a northward-younging extensional continental arc (ca. 470-280 Ma) associated with bimodal igneous activity, which indicates that the westward extension of the Solonker suture is located north of the Hongshishan-Peng-boshan tectonic zone, (4) Late Carboniferous opening and Permian north-dipping subduc-tion of the Liuyuan Ocean in the southern Beishan orogen, and (5) Mesozoic-Cenozoic intracontinental deformation induced by the final closure of the Paleo-Asian Ocean system in the north and the Tethyan Ocean system in the south.