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Precise timing of granitoids and constraints of their magma sources are critical to understanding the subduction–collision tectonic evolution of the Altun orogenic belt (AOB), a vital part of the Qinghai-Tibet plateau in northwestern China. We provide in-situ zircon U–Pb age, Hf isotopic composition and whole-rock geochemistry of the Yusupualeke granitic pluton in the South Altun orogenic belt (SAOB), an integral unit of the AOB, to determine the tectono-magmatic evolution of the SAOB at early Palaeozoic. The Yusupualeke granitic pluton comprises the medium-coarse grained porphyritic monzogranite and medium-fine grained granodiorite. The monzogranite sample yielded a weighted mean 206Pb/238U age of 476.8 ± 3.6 Ma (MSWD = 0.59), while the granodiorite yielded a weighted mean 206Pb/238U age of 453.2 ± 4.7 Ma (MSWD = 0.013). Zircon U–Pb ages suggest that the subduction–collision process of the SAOB remained from the middle stage of the early Palaeozoic to the end. Both of the studied granitoids belong to metaluminous to weakly peraluminous series and show typical I-type granite characteristics with depletions in Ba, Nb, Sr, P, and Ti, and enrichments in light rare earth elements (LREEs), Rb, Th, K, and slightly negative Eu anomalies. Based on the geochronological data and regional geological background, we believe that the porphyritic monzogranites were formed during the northward subduction process of the South Altun ocean (SAO), while the granodiorites were formed during the tectonic regime transition stage. Besides, combing the previous research achievements with our newly obtained data, we put forward a new division and geodynamic model of the early Palaeozoic tectono-magmatic evolution for the South Altun orogenic belt. [ABSTRACT FROM AUTHOR]

Data from ophiolites indicate that the Longmuco–Shuanghu Suture Zone (LSSZ) was connected with the Changning–Menglian Suture Zone (CMSZ) during the Paleozoic. Numerous geological records of late Cambrian–Silurian arc magmatism have been found along the LSSZ and CMSZ. However, all the reported early Paleozoic arc magmatism in the South Qiangtang subterrane (SQT) was based on crust-derived magmatic rocks, which constrained our acknowledge of the complicated geodynamic evolution processes. Here, we present bulk-rock geochemistry, Sr Nd isotopes, and zircon U Pb dating and Hf isotope data for a newly discovered Silurian complex in the Xiangtaohu (XTH) area of the central Qiangtang Terrane, central Qinghai–Tibetan Plateau, to investigate the magmatic and tectonic evolution of the LSSZ and CMSZ. The XTH complex is composed of diorite, monzogranite, and biotite monzogranite. Zircon U Pb dating results show that the XTH complex was emplaced at 438–429 Ma. The diorites belong to the calc-alkaline to high-K calc-alkaline series, showing metaluminous to weakly peraluminous features. All of the granites are high K, calc-alkaline, and weakly peraluminous. The diorites have low initial 87Sr/86Sr ratios (0.704526–0.705002) and ε Nd (t) values (−1.32 to 0.12), with zircon ε Hf (t) values ranging from −1.2 to 0.4, indicating a metasomatic mantle source with subducted-sediment-derived melts, and low MgO, Mg#, Cr, and Ni values, reflecting crystal fractionation from basaltic magma. The monzogranites and biotite monzogranites show I-type granite geochemical affinity, with slight negative ε Nd (t) values (−2.03 to −1.67) and low initial 86Sr/86Sr values (0.704056–0.705165), with zircon ε Hf (t) values ranging from −3.1 to 4.8, suggesting that they were derived mainly from partial melting of juvenile mafic lower crust. The samples are enriched large-ion lithophile elements, depleted high-field-strength elements, and have high U/Yb ratios of zircons, suggesting that the XTH complex was formed in a continental arc setting. The XTH Silurian complex is the youngest magmatic record of the southward subduction of the Longmuco–Shuanghu Prototethys oceanic plate, which represent the melting productions of the mantle wedge and mafic lower crust. It is different from the previously discovered S-type granites in the same area. Combining our new results with comprehensive existed data in the region, we propose that the Changning–Menglian Prototethys oceanic plate subducted beneath the Baoshan block (eastward) and the Yangtze block (westward) during early Paleozoic, while the Longmuco–Shuanghu Prototethys oceanic plate only subducted southward under the southern Qiangtang subterrane. [Display omitted] • Newly discovered Silurian magmatic complex developed at Xiangtaohu area in the LSSZ. • The Xiangtaohu complex has continental margin arc affinity. • Arc magmatic rocks derived from melting of mantle wedge and basic lower crust. • The southward subduction of the LSTO lithosphere. [ABSTRACT FROM AUTHOR]

The widespread Tibetan Permo‐Carboniferous glaciogenic diamictites (PCGDs) are conventionally thought to be sourced from Indian Gondwana during glacier transport and deglaciation. However, the Lhasa PCGDs differ in detrital zircon U‐Pb age spectra and εHf(t) values from those in Southern Qiangtang and Tethyan Himalaya. The similarities in εHf(t) values for similar‐age detrital zircons, the development of glacier transport pathways, and the large volumes of the Tibetan PCGDs indicate an Australian source for the Lhasa PCDGs, and an Indian source for the Southern Qiangtang and Tethyan Himalayan PCDGs. We conclude that the Southern Qiangtang and Tethyan Himalayan are paleographically linked to northern India, whereas Lhasa is positioned adjacent to NW Australia during the Paleozoic. Magmatic and metamorphic records further indicate that eastern Lhasa (E90°–E95°) represents the outboard extension of events recorded in northern Central Australia, whereas western Lhasa (E80°–E90°) was located outboard of the West Australian Craton. Plain Language Summary: Precisely understanding the paleogeography of the Lhasa Terrane in southern Tibet is crucial to reconstruct the opening and drifting histories of the Neo‐Tethys that controls on the evolution of the India‐Asia collision zone. The paleogeography of the Lhasa Terrane has been variously proposed to originate from northern India, northwest Australia, and the northern extent of the East African Orogen. Resolving this paleogeographic puzzle requires solid lines of evidence and a full understanding of the data. A combination of new detrital zircon U‐Pb age and Hf isotope data of the Tibetan Permo‐Carboniferous glaciogenic diamictites constrains the paleogeography of the Lhasa Terrane to a position adjacent to NW Australia. Magmatic and metamorphic records further refine that the eastern Lhasa (E90°–E95°) represents the outboard extension of events recorded in northern Central Australia, whereas the western Lhasa (E80°–E90°) was located outboard of the West Australian Craton. Our results show that a combination of provenance analysis (including magmatic history, isotopic data, and sediment transport pathway) of the widespread late Paleozoic diamictites in Gondwana, as well as magmatic and metamorphic records, can allow precise paleogeographic reconstruction of the longitudinal disposition of blocks along the northern Gondwana margin. Key Points: Lhasa Permo‐Carboniferous glaciogenic diamictites (PCGDs) differ in detrital zircon U‐Pb age and εHf(t) from those in S. Qiangtang and Tethyan HimalayaLhasa PCGDs come from Australian Gondwana, whereas the S. Qiangtang and Tethyan Himalayan PCGDs from Indian GondwanaE. Lhasa represents the outboard extension of N. Central Australia, whereas W. Lhasa was located outboard of the West Australian Craton [ABSTRACT FROM AUTHOR]