Late Triassic paleolatitude of the Southern Qiangtang terrane, central Tibet: Implications for the closure of the Longmu Co-Shuanghu Paleo-Tethyan Ocean

Abstract

Studies on the paleogeographic evolution of the Southern Qiangtang terrane, as an integral component of the Cimmerian continent, are essential for understanding the geodynamic evolution of the Tethys domain. Here, we present a paleomagnetic study of Late Triassic volcanics (∼222–206 Ma) from the Southern Qiangtang terrane, with the aim of enhancing our understanding of the evolutionary processes of the Longmu Co-Shuanghu Paleo-Tethyan Ocean. The characteristic remanent magnetizations (ChRMs) carried by magnetite and hematite, which formed during the high-temperature oxidation in the initial cooling phase of the volcanic rocks, are effectively isolated through successive thermal demanetizations. The ChRMs pass the fold test, indicating a primary magnetization. It appears to average out paleosecular variation well enough to yield a reliable paleolatitude estimate. Following tilt correction, the ChRMs yield an overall mean direction of Ds = 185.4°, Is = 53.8°, ks = 94.3, α95 = 3.8°, N = 16, indicating a paleolatitude of 34.3°N and a paleopole located at –22.5°N, 82.9°E with A95 = 4.4°. Comparing the Triassic latitudinal history of the Southern Qiangtang with that of the Northern Qiangtang suggests that the western part of Longmu Co-Shuanghu Paleo-Tethyan Ocean likely closed during the early Late Triassic. Moreover, integration with other geological evidence from the Southern Qiangtang terrane suggests that the Longmu Co-Shuanghu Paleo-Tethyan Ocean closed diachronously from east to west.