Palaeomagnetic constraints on a Late Permian to Early Triassic final closure of thePalaeo‐AsianOcean

Abstract

AbstractFinal closure of the Palaeo‐Asian Ocean signifies the ultimate amalgamation of the North China, Tarim, Mongolia, Songliao, Xilinhot and other Central Asian blocks, and therefore, is critical in reconstructing the configuration of the Pangea supercontinent during the late Palaeozoic to early Mesozoic. However, the final closure time remains contentious. Here, we present a systematic palaeomagnetic study on the Upper Permian sedimentary sequences of the Xilinhot Block, located to the north of the Solonker Suture Zone. Rock magnetic results indicate stable pseudo‐domain magnetite is the dominant magnetic carrier. The characteristic components isolated between ~350 and 590°C display the existence of dual polarities. Combined with previous results, the merged site‐mean directions yield a negative reversal test and inconclusive fold tests. By comparing with coeval and posterior data, and correlating with stitching plutons that intruded the sampling sections, we argue for a remagnetization origin for the newly obtained data, which is most likely acquired during the thermal event when the stitching granitic plutons intruded at 242.0 ± 3.7 Ma. Then we synthesized available palaeomagnetic data from the Central Asian Orogenic Belt and adjacent blocks, and propose a Late Permian to Early Triassic final closure of the Palaeo‐Asian Ocean. Our reconstruction of Pangea in the Early Triassic negates the existence of a cut‐through seaway between the Mongol‐Okhotsk and Palaeo‐Asian Oceans. The Mongol‐Okhotsk Ocean was an extension of Panthalassa, in trumpet‐shaped and faced to the east, rather than an individual oceanic basin separating Siberia from the Cinamuria Block.