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To determine the Late Palaeozoic evolution of the Lhasa terrane, we report the results of field mapping, petrological and fossil investigations, and U–Pb dating of detrital zircon grains (n = 474) from lower-greenschist-facies clastic rocks of the Lagar Formation in the Baruo area, Tibet. Our results indicate that the Lagar Formation was deposited during the Late Carboniferous to Early Permian in a shallow-marine environment on the northern margin of Gondwana. Glacial marine diamictites are common within the Lagar Formation and record glaciation of Gondwana during the Late Palaeozoic. Moreover, the detrital materials of the Lagar formation originated mostly from the collision orogenic belt. The ages of detrital zircon grains from the Lagar Formation make up five main groups with ages of 410–540 Ma, 550–650 Ma, 800–1100 Ma, 1600–1800 Ma, and 2300–2500 Ma, which display three characteristic age peaks at ~1150, 2390 and 2648 Ma. We tentatively suggest that the Lhasa terrane was a shallow-marine basin under the influence of the Gondwanan glaciation during the Late Carboniferous–Early Permian. [ABSTRACT FROM AUTHOR]

As a part of the Bangong-Nujiang suture, the Shiquanhe-Namco ophiolite mélange belt (SNM), together with the Bangong-Nujiang ophiolite mélange belt (BNM), records the evolutionary history of the Mesotethys. In terms of the closure of the Mesotethys, previous sedimentological research has focused on the BNM, while the SNM remains insufficient. On the basis of detrital zircon dating and sedimentologic data, in this study, we determined the existence of Aptian deep-marine turbidites in the Zhongcang and Lhakorco areas of the SNM. Sandstone petrographic and detrital zircon analysis combine to show that the Zhongcang turbidites provide records of the recycled from the accretionary complex and Triassic-Jurassic strata in the southern Qiangtang margin, with the minor addition of Qiangtang magmatic arc rocks, while sediments in the Lhakorco turbidites were derived mainly from recycled orogen source and Late Jurassic-Early Cretaceous magmatic arc in the Lhasa Terrane. Further analysis suggests that the Aptian turbidites were deposited in a deep-marine oceanic basin of Mesotethys and this oceanic basin prevented Qiangtang-derived sediments transported onto the Lhasa terrane. The Mesotethys experienced diachronic closure from east to west during the Early Cretaceous, and the final closure was most likely completed along the SNM after Aptian. • Discovery of the Aptian deep-marine fan turbidities in SNM • Featuring the Aptian Qiangtang and Lhasa source separation along SNM • Implications for diachronous closure of the Mesotethys [ABSTRACT FROM AUTHOR]