Late Early Paleozoic and Early Mesozoic intracontinental orogeny in the South China Craton: Geochronological and geochemical evidence

Abstract

The late Early Paleozoic and Early Mesozoic tectonic events in South China have been central to the debate over plate subduction versus intracontinental orogeny. Here we present zircon U–Pb geochronology, Hf isotopes and whole-rock geochemistry of six representative granitic plutons from South China. The zircon data show two groups with 206Pb/238U ages of ca. 430Ma and 225Ma, representing the crystallization ages of magma. The six plutons investigated in this study are characterized by peraluminous nature with high A/CNK values (>1.1) and the presence of aluminous minerals like muscovite. They exhibit enrichment in LREE, depletion in Eu, negative Ba, Sr, Nb and Ti anomalies and enrichment in Rb, Th, U and Pb. All samples show variably negative εHf(t) values (−2 to −16) with two-stage Hf model ages clustered around 1.5–1.8Ga. These data indicate that both the Early Paleozoic and Early Mesozoic granitic magmas were generated by the partial melting of early-middle Paleoproterozoic basement rocks without significant input of mantle material. The distribution of all the plutons with ages around 430Ma and 225Ma are unrelated to subduction tectonic regime. Combining with other geological evidence, our study suggests that the tectono-magmatic events during late Early Paleozoic and Early Mesozoic were largely related to intracontinental orogeny triggered by interactions between the Yangtze and Cathaysia continental blocks. The far-field stress propagation derived from the South China plate boundary might have played a crucial role as the primary cause of the stress field within the continental interior of the South China Craton.