Newly discovered early Neoproterozoic (ca. 900 Ma) andesitic rocks in the northwestern Tarim Craton: Implications for the reconstruction of the Rodinia supercontinent

Abstract

The Tarim Craton, one of the largest continental blocks in China, has been considered as a constituent block of the Rodinia supercontinent. However, the early Neoproterozoic tectonic evolution and the role of the Tarim Craton in the reconstruction of Rodinia remain controversial. Here, we present zircon U-Pb and Lu-Hf isotopic and whole-rock geochemical data for the newly discovered andesitic rocks in the Aksu area of northwestern Tarim Craton. LA-ICP-MS zircon dating results show that they were formed at ca. 908–903 Ma. These andesites have arc-type geochemical features such as enrichment in LREEs with (La/Yb)N ratio of 4.4–6.9 and obviously negative Nb, Ta, Ti anomalies. The high positive zircon εHf (t) (+7.5 to +11.9) values, integrated with trace element signatures, indicate that the magma source of the andesitic rocks were derived from partial melting of mantle wedge that was metasomatized by the sediment/slab-derived fluids through subduction, with possibly insignificant contributions from crustal materials. These geochronological and geochemical data suggest that subduction-related arc magmatism occurred in the northwestern Tarim Craton as early as ca. 900 Ma. Combined with a compilation of previous published data, these results therefore indicate that active continental margin probably widely occurred along the northwestern and southeastern margins of the Tarim Craton and adjacent microcontinents during the early Neoproterozoic, which may be linked to the Neoproterozoic circum-Rodinia subduction-accretion system.