Paleomagnetic Data On The Late Paleozoic—Early Mesozoic Rocks Of Central Qinghai-Tibet Plateau, China

The geological structure and tectonics of the Qinghai-Tibet Plateau is closely related to the collision between the Gondwanaland and Eurasia plates since the Paleozoic. The tectonic kinematics process of the collision and collage between the main blocks within the plateau was not sure, the evolution histories of the Tethys ocean basins among the Indian plate and Tarim block, however, is not clear. Furthermore, plate boundary between the Gondwanaland and Eurasia plates is highly debated. This study try to restore the relative position of the main blocks (e.g. northern Qiangtang, southern Qiangtang and Gangdese) of the Qinghai-Tibet Plateau in the Late Paleozoic to Early Mesozoic periods, and to ascertain the deep significance of the Longmuco-Shuanghu-Lancangjiang suture zone and the Bangonghu-Nujiang suture zone which divided the three blocks in the issue of plate boundary between the Gondwanaland and Eurasia, as well as rebuild the movement process (such as distance, speed and rotation) of the northern Qiangtang, southern Qiangtang and Gangdese blocks in the northward displacement, using paleomagnetism as the main research method. We present new high-precision paleomagnetic data, which provide critical insights for our understanding of paleogeographic positions and subsequently-occurred tectonic evolution history of the main blocks in the Qinghai-Tibet Plateau, and provide an important reference for understanding the plate boundary between the Gondwanaland and Eurasia plates.Based on the new data obtained in rocks of the northern Qiangtang-Qamdo block, we built the apparent polar wander path (APWP) in Late Carboniferous to Middle Jurassic, and discussed the kinematics process. Our study suggests that:(1) the Qamdo and northern Qiangtang blocks were paleogeographically situated at low to intermediate latitudes in the southern hemisphere in the Late Carboniferous-Late Permian periods, they may have been independent of each other during this periods. They successively occured counter-clockwise rotation (about40°) in the Middle-Late Permian, and involved in the continent-continent collision stage in the Late Permian-Early Triassic periods, built a consolidated northern Qiangtang-Qamdo block.(2) The northern Qiangtang-Qamdo block began to drift northward in the Early Triassic, the average movement speed of about6.2cm/a in the Early Triassic to Late Triassic periods, with clockwise rotation of about70°, reach about17.9°N in the Late Triassic, and reach about24.3°N in the Middle-Late Triassic, the average movement speed in the Late Triassic to Middle-Late Triassic periods is about lcm/a. A latitudinal motion of about900km from current location was taken place after Middle-Late Triassic.A set of preliminary research results in the Gangdese block were also been gained. The Gangdese block situate at15.7°S in the Triassic according to our paleomagnetic data. By comparison with the paleomagnetic results in the northern Qiangtang-Qamdo block, we suggest that both the two blocks might geographically situated at low to intermediate latitudes in the southern hemisphere in the early Triassic, the northern Qiangtang block drift northward quickly relative to the Gangdese block in the Middle to Late Triassic period, with a distance of about2900km, accompanied withclockwise rotation of about61°.