The Cretaceous stationary Lhasa terrane constrained by the paleolatitude of 103 Ma volcanic rocks from the Nima area

摘要

To constrain the paleolatitude evolution and orientation of the Lhasa terrane in the Cretaceous, we performed a paleomagnetic study on the Qushenla Formation volcanic rocks dated to-103 Ma near Nima County in the central part of the Lhasa terrane. Rock magnetism and magnetic petrography indicate that the primary magnetic carriers are magnetite and hematite that formed during initial cooling. A high-temperature component was isolated between-500 degrees C and-680 degrees C. The site-mean direction passes the fold tests at a 99% confidence level, yielding a mean inclination of 35.4 degrees for 18 sites after tilt correction. These results suggest that the volcanic rocks recorded a primary remnant magnetization, revealing a paleolatitude of-17.9 degrees N at-103 Ma for the reference point (29.0 degrees N, 87.5 degrees E) at the southern margin of the Lhasa terrane. Together with previous paleomagnetic results from the Lhasa terrane, our results indicate WNW-ESE elongation of the stationary Lhasa terrane at-6.7-19 degrees N during the Cretaceous. The paleolatitude evolution of the Lhasa terrane during the Jurassic-Cretaceous suggests that the Lhasa-Qiangtang collision occured at-155-132 Ma.