Multistage Neoproterozoic granitic magmatism and formation of Yidong tin deposit in northern Guangxi, China

A Neoproterozoic tin ore cluster, which is rare for South China, has been discovered in northern Guangxi. The Neoproterozoic granite pluton was formed through multistage magmatism. Previous work suggested that the tin mineralization in this region is genetically related to early-stage granitic activity, which is inconsistent with the classical understanding that tin mineralization is mainly linked to late-stage magmatic activity. The relationship between the formation and evolution of Neoproterozoic granite pluton and tin mineralization in northern Guangxi remains unclear. The Pingying granite pluton, associated with the large-scale Yidong tin deposit, is divided into coarse-grained, medium-grained, and medium-fine-grained granites from the center to the margin. Notably, an intrusive contact relationship exists between coarse-grained and medium-fine-grained granites, which provides an excellent window to reveal the relationship between Neoproterozoic pluton evolution and tin mineralization. Here, we present zircon and cassiterite U–Pb ages, whole-rock major- and trace-element compositions, and zircon Hf isotopic data for the pluton. Zircon U–Pb ages are 835.5 ± 3.0 Ma for the coarse-grained granite and 814.6 ± 7.9 Ma for the medium-fine-grained granite. Cassiterite yields a U–Pb age of 815.2 ± 8.2 Ma, consistent with that of the medium-fine-grained granite. The coarse-grained and medium-fined-grained granites have similar zircon εHf(t) values and TDM2 ages, ranging from −8.1 to −1.1 and 1.78 to 2.24 Ga, respectively. The Granites are plotted in the domains of melts derived from partial melting of metapelitic rocks on the Al2O3/TiO2 vs. CaO/Na2O, Rb/Sr vs. Rb/Ba, and C/MF vs. A/MF diagrams, suggesting the pluton formed by partial melting of Mesoproterozoic to Paleoproterozoic metapelite and underwent high fractional crystallization. Geochemical data indicate strong K-feldspar fractional crystallization from the early stage to late stage, resulting in a higher fractionation and magmatic evolution in late-stage granites compared to early-stage granite. These features demonstrate a genetic link between tin mineralization and late-stage magmatism. Tin deposits in northern Guangxi predominantly formed in association with late-stage magmatic activities during the Neoproterozoic. Exploration should target late-stage highly fractionated granites.