Paleomagnetic data bearing on the Mesozoic deformation of the Qiangtang Block: Implications for the evolution of the Paleo- and Meso-Tethys

Paleomagnetism has played an important role in quantifying the Mesozoic evolution of "Proto-Tibet". In this paper, we present new paleomagnetic data from five Middle-Upper Jurassic sedimentary sequences (Quemo Co, Buqu, Xiali, Suowa and Xueshan Fms.) of the eastern North Qiangtang Terrane (QT) at Yanshiping (33.6 degrees N, 92.1 degrees E). The new paleomagnetic results form a large dataset (99 sites, 1702 samples) and reveal a paleopole at 79.1 degrees N/306.9 degrees E (dp = 3.9 degrees, dm = 6.3 degrees) for the Quemo Co Fm., at 68.9 degrees N/313.8 degrees E (dp = 2.1 degrees, dm = 3.7 degrees) for the Buqu Fm., at 66.1 degrees N/332.1 degrees E (dp = 2.7 degrees, dm = 4.6 degrees) for the Xiali Fm., at 72.4 degrees N/318.6 degrees E (dp = 3.9 degrees, dm = 6.7 degrees) for the Suowa Fm., and at 76.9 degrees N/301.1 degrees E (dp = 7.9 degrees, dm = 13.2 degrees) for the Xueshan Fm. These results indicate clockwise (CW) rotations of similar to 19.8 +/- 9.4 degrees between similar to 171.2 and 161.7 Ma and counterclockwise (CCW) rotations of similar to 15.4 +/- 13.4 degrees between similar to 161.7 and <157.2 Ma for Yanshiping. We attribute the change in rotation sense at approximately similar to 161.7 Ma to the initial collision of the Lhasa and Qiangtang terranes. Using this and other paleomagnetic data from the Lhasa, Qiangtang and Tarim terranes, as well as other geological evidence (e.g., tectonism-related sedimentary sequences, volcanism, and HP metamorphism), we propose a new conceptual evolution model for the Mesozoic QT and Tethyan Oceans. The Longmo Co-Shuanghu oceanic slab was subducted before 248 Ma, followed by continental collision of the North-South Qiangtang subterranes between similar to 245 and 237 Ma. The Qiangtang Terrane experienced post-collisional exhumation between similar to 237 and 230 Ma during subduction of the Jinsha oceanic slab. The collision of the Qiangtang and Songpan-Ganzi terranes occurred between similar to 230 and 225 Ma. The QT experienced post-collisional relaxation from similar to 225 to similar to 200 Ma, followed by subsidence and extension-related exhumation between similar to 200 and 162 Ma in association with subduction of the Bangong-Nujiang oceanic slab. Finally, these events were followed by the scissor-like diachronous collisions of the Lhasa and Qiangtang terranes between similar to 162 Ma and the mid-Cretaceous. (C) 2016 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.