1.4 Ga metabasites in the South China block: Insights into its mesoproterozoic geological evolution

Abstract

The paleogeographic reconstruction of the Paleo-Mesoproterozoic Nuna/Columbia supercontinent is less well constrained compared to that of younger supercontinents (e.g., Rodinia, Gondwana, Pangea). For instance, the precise paleoposition of the Cathaysia Block within Nuna remains uncertain. This challenge is partly due to the scarcity of relative paleontological and precise paleomagnetic data, along with limited geological records extending into deep time. Here, we identified a suite of Mesoproterozoic metabasites on the Hainan Island in the southern margin of Cathaysia Block. Zircon UPb dating constrains the studied rocks formed at ∼1.43 Ga, with distribution patterns of rare earth elements resembling enriched mid-ocean ridge basalt and significantly negative NbTa anomalies in the spider diagram. Additionally, Mesoproterozoic metabasites were characterized by radiogenic zircon Hf (ε_Hf(t) > 0) and whole-rock Nd (ε_Nd(t)) > 0) isotopes, indicating that they originated from a depleted mantle source. Given that these metabasites concurrently occurred with A-type granitic rocks in the studied region, we propose that they were most likely produced in an intraplate rift setting, corresponding to the breakup of the Nuna supercontinent. Furthermore, we compiled zircon UPb isotopic data from Mesoproterozoic sedimentary rocks across other cratonic blocks. Provenance statistical analysis of this data showed that the Cathaysia Block shares a positional affinity with Mawson and Laurentia.