Reconstructing Tarim within Rodinia: Constraints from early Tonian accretionary and collisional records in the Altyn belt

The position of the Tarim craton within Rodinia has long been debated, with competing models varying from internal to external ones. The Altyn belt in the southeast Tarim margin preserves extensive early Neoproterozoic magmatic successions, which are possibly related to the Rodinia assembly. Thus, we here investigated the granitoids in the South Altyn belt (SAB), and present field geology, zircon U–Pb–Hf–O isotopes and H₂O contents, and whole rock geochemistry data from these granitoids. The Tula granite is dated at 914 ± 3.9 Ma, whereas the Kuoshi granites are dated at 919 ± 5.2 Ma and 927.7 ± 5.0 Ma. The Tula and Kalaqiaoka granite samples display high ACNK values that are typical of S-type granitoids, consistent with the occurrence of garnet and muscovite. In addition, the Tula granite has higher zircon δ¹⁸O (7.62 to 10.85 ‰) and lower εHf(t) (−2.4 to +0.1) values, along with lower zircon H₂O content (medium values at 102 ppmw), indicating a primary water-deficient magma generated from recycled ancient crust, with minor juvenile contribution. On the other hand, the Kuoshi granite shows high Sr (169–259 ppm), Sr/Y (17.85–19.33) and (La/Yb)_N (30–49) ratios. The Kuoshi granites are also characterized by higher MgO, lower zircon δ¹⁸O (4.15 to 9.81 ‰) and εHf(t) (−4.0 to −0.4) values, higher zircon H₂O content (medium values at 255 ppmw), as well as subduction related chemical features. These signatures suggest that the Kuoshi granitic magma might have been formed by partial melting of recycled ancient crust and juvenile crust in a subduction setting. Thus, these granitoids across the SAB reflect a transformation from water-enriched subduction setting to water-deficient syn-collisional setting at ca. 930–920 Ma. Moreover, the zircon Hf isotope evolution trend across the SAB also suggest a possible transformation from slab retreat to syn-collision at 930–920 Ma. Furthermore, the end Mesoproterozoic and early Neoproterozoic metamorphic and magmatic events in the Tarim Craton, North Qaidam-Kunlun Block, Australia and India blocks display a close affinity. Therefore, we conclude a position of the Tarim craton between QKB, Australia and North India blocks in the periphery of Rodinia, consistent with earlier paleomagnetic data.