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Chronology, geochemical characteristics, and tectonic implications of a Triassic complex in the Rongma Area, Southern Qiangtang, Tibet TEXT SIZE: A A A
The spatio-temporal evolution of the Paleo-Tethys Ocean has been a hot and controversial issue in the world. Here we carry out petrographic, chronological, and geochemical study on garnet-phengite-quartz schist and mafic rocks in the Rongma area from the northern margin of the Southern Qiangtang block to determine the early Mesozoic tectonic evolution of the Shuanghu Paleo-Tethys Ocean in northern Tibet. The zircons from a phengite-quartz schist sample yielded concordant ages of 1936-393 Ma, indicating that its protolith deposited after similar to 393 Ma. Overgrowth zoning garnet with three stages of metamorphic evolution from garnet core to rim (i.e., Peak metamorphic, early retrograde metamorphic, and late retrograde metamorphic stages) in the schist was recognized, indicating that two subduction in a short time might be involved for its genesis. Two groups of phengite in the schist yielded Ar-40/Ar-39 plateau ages of 229 +/- 1.4 Ma and 225 +/- 1.3 Ma, respectively; thus, the late retrograde metamorphism of the schist might occur at similar to 229-225 Ma. Zircon U-Pb dating of a diabase in the area yielded crystallization age of 241 +/- 1.1 Ma implying its formation in the early Triassic. The Hf-in-zircon and whole-rock Nd isotopes of the diabase show epsilon(Hf)(t) of - 0.6- + 19.1 and epsilon(Nd)(t) of - 0.8 to + 0.9, respectively. Combined with the whole-rock geochemical features of the early Triassic diabase (241 Ma) and gabbro (237 Ma), they indicate that these mafic rocks are formed in a back-arc extensional setting related to the subduction of the oceanic plate between the Northern and Southern Qiangtang blocks beneath the latter. Combined with regional data, our study favors that view bi-directional subduction of the Shuanghu Paleo-Tethys ocean in the Early Triassic and it was finally closed at similar to 237 to similar to 229 Ma. Our model will help us better understand the tectonic evolution of the Paleo-Tethys Ocean.

Publication name

INTERNATIONAL JOURNAL OF EARTH SCIENCES, Volume 111, Issue 4, Page 1079-1106, DOI 10.1007/s00531-021-02129-2, Published JUN 2022, Early Access MAR 2022


Fan, Zheng-Zhe; Wang, Quan; Chen, Xian; Wang, Gen-Hou; Fu, Yue; Guo, Gui-Juan

Corresponding author(s) 

Wang, Quan
China Geol Survey, Dev & Res Ctr, Beijing 100037, Peoples R China

Chen, Xian
Chinese Acad Sci, Inst Geochem, Guiyang 550081, Peoples R China

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