Multi-stage magmatism and Sn-polymetallic mineralization in the Shuicheng Region, SW China

The economically important tin‑tungsten mineralization in southwestern China has attracted much interest in recent years, yet its age, tectonic setting, and genetic relationship to the host granites remain uncertain in most regions. Our focus in this study is the Shuicheng tin-polymetallic deposit, situated in the western sector of the Diantan Batholith, within the northern Tengchong Block. The granites in this area consist of two intrusive units, i.e., 1) biotite monzogranite (T1), with LA-ICP-MS zircon UPb ages ranging from 76.88 ± 0.43 Ma to 74.69 ± 0.57 Ma, whole-rock εNd(t) values ranging from −9.75 to −8.11, and zircon εHf(t) values from −12.19 to −8.85; and 2) alkali-feldspar granite (T2), with an LA-ICP-MS zircon UPb age of 52.16 ± 0.23 Ma, whole-rock εNd(t) values of −10.15 to −8.25, and zircon εHf(t) values of −9.64 to −8.06. These two intrusive events have been linked to prolonged low-angle subduction and retreat of the subducting Neo-Tethys Ocean Plate, respectively. The Shuicheng granites exhibit high concentrations of SiO2 and Al2O3, contrasted with low levels of FeOT, CaO, MgO, TiO2, and P2O5, suggesting that they are highly fractionated S-type granites. High abundances of Rb, K, U, and Hf, along with low contents of Ba, Sr, and Ti, further indicate significant fractionation and crystallization processes during magma evolution. Importantly, a transition from purely magmatic conditions to a magmatic-hydrothermal state occurred during the latter stages of magmatic evolution. This transition, associated with an amplified potential for tin mineralization, provides fresh insight into the role of magmatic processes in ore genesis, enriching our understanding of the tin‑tungsten mineralization history of the Tengchong region.