New Middle Jurassic Paleomagnetic and Geochronologic Results From the Lhasa Terrane: Contributions to the Closure of the Meso‐Tethys Ocean and Jurassic True Polar Wander.

The drift history of the Lhasa terrane is crucial for understanding the tectonic evolution of Tethyan Oceans and Jurassic true polar wander. However, high‐quality Middle Jurassic paleomagnetic data from the Lhasa terrane are limited in number. Here we report a combined paleomagnetic and geochronologic study on the Yeba Formation volcanic rocks, dated at ∼170 Ma, from the Lhasa terrane. Robust field and reversal tests indicate that the characteristic remanent magnetizations are primary. Our results provide a reliable Middle Jurassic (∼170 Ma) paleopole at 29.8°N, 180.7°E with A95 = 5.7° and a paleolatitude of 14.4 ± 5.7°N for the Lhasa area. Compared with previous paleomagnetic and geologic evidence, we propose that the Meso‐Tethys Ocean probably began to close in the eastern part at ∼168 Ma and that the Lhasa terrane underwent a ∼2,900 km southward "monster shift" during the Late Jurassic. Plain Language Summary: The formation of the Tibetan Plateau followed the breakup of the Gondwana supercontinent and was associated with the demise of several Tethyan Oceans. The Lhasa terrane, which is a long and narrow continental fragment derived from Gondwana, was isolated in the Tethyan Ocean during the Jurassic and finally accreted to the south margin of the Paleo‐Asia continent, leading to the closure of the Meso‐Tethys Ocean. However, when this Meso‐Tethys Ocean closed is still controversial. Our new robust paleomagnetic result shows that the Lhasa terrane was located at ∼14.4°N at ∼170 Ma. Based on available reliable Jurassic paleomagnetic data from the eastern part of the Lhasa and Qiangtang terranes, we suggest that the Meso‐Tethys Ocean began to close in the eastern part at ∼168 Ma. Integrating our critical Middle Jurassic paleomagnetic data with that of the Late Jurassic from the Lhasa terrane, we argue that the Lhasa terrane suffered a ∼2,900 km southward latitudinal shift during the Late Jurassic, which is known as true polar wander. Key Points: The Lhasa terrane was located at ∼14.4 ± 5.7°N at ∼170 MaThe Lhasa terrane experienced a ∼2,900 km southward monster shift during the Late JurassicThe closure of the Meso‐Tethys Ocean in the eastern part most likely occurred at ∼168 Ma [ABSTRACT FROM AUTHOR]