Cassiterite and monazite U-Pb dating, and cassiterite geochemistry of the Shiganghe and Tiechang tin deposits in the Baoshan district (NW Yunnan), SW China

The Baoshan district in the southwestern Sanjiang Tethyan domain is an important part of the worldclass Southeast Asian tin (Sn) belt. However, the timing and controlling factors of Sn mineralization are poorly constrained. Here, we conducted laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb dating of cassiterite and monazite, and cassiterite trace element analysis on the Shiganghe and Tiechang Sn deposits (Baoshan district) to unravel the temporal evolution of the regional Sn mineralization. The U–Pb dating of two cassiterite samples from Shiganghe yielded Tera-Wasserburg lower intercept ages of 75.5 ± 3.9 Ma and 75.9 ± 4.8 Ma. U-Pb dating on cassiterite and the cogenetic monazite from Tiechang yielded 32.8 ± 1.3 Ma and 32.2 ± 1.0 Ma, respectively. These ages confirm both Late Cretaceous and Oligocene Sn mineralization events in the Baoshan district. Geological characteristics, and age and geochemical data of cassiterite indicate that Shiganghe is a quartz-vein-type Sn deposit, genetically related to the Late Cretaceous granite that intruded the Ordovician Zhibenshan pluton. Tiechang resembles distal skarn Sn deposits related to the 32 Ma magmatism along the Chongshan shear zone. Tin mineralization in the Tengchong-Baoshan district occurred mainly from the Late Cretaceous to Oligocene, corresponding to the Neo-Tethyan subduction and the subsequent India–Asia continental collision.