~790 Ma OIB-type mafic dykes in the North Altyn Block, southeastern Tarim: insights into the reconstruction and geodynamics of Rodinia breakup

Deciphering the extensive magmatic records of the Rodinia supercontinent preserved within the Tarim Craton provides valuable insights into the geodynamics of supercontinent evolution. Here, we report ~790 Ma OIB-type mafic dykes from the North Altyn Tagh belt in the southeastern margin of the Tarim Craton. Zircon U-Pb dating and geochemical analyses reveal that these dykes are typical continental flood basalts, which display light rare earth elements (LREE) enriched patterns with Eu depletion, along with slight enrichment of Nb and Ta and depletion of Sr. Chemical and thermodynamic modelling suggest that these mafic dykes were originated from a garnet-spinel mantle source modified by subduction-related fluids, with an estimated partial melting degree of ~10%. This was followed by fractional crystallization of Ol-Cpx-Pl during subsequent magma evolution process. Therefore, the OIB dykes identified here indicate that the Tarim Craton had already rifted from Rodinia, likely around ~790 Ma. This, together with review of overall Neoproterozoic magmatic records across the Tarim Craton, along with detrital zircon ages and Hf isotopic data, demonstrates that the craton preserves complete record of the transition from Rodinia convergence to rifting. Moreover, the Tarim Craton, Central Altyn, Qilian-Qaidam-East Kunlun, Yangtze Block and Cathaysia Block were located along the periphery of Rodinia and all recorded the super-mantle plume that broke the Rodinia supercontinent at 850–740 Ma. The plume activity partially overlapped with circum-Rodinia subduction. Overall, the contribution of subduction fluid to Rodinia OIB type plume magmatism and the spatial-temporal correlation of super mantle plume and circum-Rodinia subduction suggest that the Rodinia breakup mantle plume was likely induced by circum-Rodinia subduction. These findings therefore argue for the "top-down" model for supercontinent breakup dynamics, emphasizing the critical role of subduction-induced mantle plume that broke up the Rodinia supercontinent. This study demonstrates that subduction drives supercontinent fragmentation, clarifying how subduction zones and mantle plumes interact within Earth's supercontinent cycles.This research is funded by the NSFC Grants (42322208), National Key R&D Program of China (2023YFF0803604), the Natural Science Foundation of Shaanxi Province (2023JCXJ‐20 and 2021JCW‐18), the Project (JLFS/P-702/24) of Hong Kong RGC Co-funding Mechanism on Joint Laboratories with the Chinese Academy of Science, and the State Key Laboratory of Continental Dynamics (201212000174).