New Permian Paleomagnetic and Geochronologic Results From the Alxa Block: Constraints on Its Tectonic Affinity and the Closure of Paleo-Asian Ocean

Abstract

The Paleo-Asian Ocean's (PAO) closure timing and the Alxa Block's (ALB) tectonic affinity remain debated. We present new paleomagnetic and geochronologic data from Permian volcanic and sedimentary rocks in the ALB. Characteristic remanent magnetization (ChRM) directions from Early (∼282 Ma), Middle (∼268 Ma), and Late Permian (∼255 Ma) rocks pass fold, reversals, and conglomerate tests, confirming their primary origin. These results yield the first reliable Permian paleopoles for the ALB. The data indicate minor movement during the Early–Middle Permian, followed by rapid northward drift and ∼53.8° counterclockwise rotation in the Middle-Late Permian. Comparison with surrounding blocks suggests the ALB was tectonically linked to North China but independent of Tarim. A significant paleolatitudinal gap between North China–ALB and Siberian–South Mongolia blocks during the Late Carboniferous–Middle Permian implies a wide mid-eastern PAO, which closed during the Late Permian. These findings refine Permian paleogeographic reconstructions of Eastern Asia.