Geochemical Characteristics and Timing of Sn Mineralization From Yunling Tin Deposits, SW China: Insights for Ore‐Forming Processes

The tin (Sn) deposits in western Yunnan, constituting a vital component of the Southeast Asian Metallogenic Belt, exhibit inadequately constrained genetic mechanisms underlying Cenozoic Sn mineralization. This study integrates U–Pb geochronology, in situ trace element geochemistry, and oxygen isotopic analysis of cassiterite from the Yunling tin deposit. Tera‐Wasserburg lower‐intercept ages for samples ULC‐1 (17.5 ± 1.9) Ma and ULC‐3 (23.44 ± 0.82 Ma) demonstrate temporal coincidence with the regional strike‐slip shear belt activation during the Early Miocene. Cassiterite oxygen isotopes yielded δ 18 O fluid values of 7.37‰–9.22‰, suggesting that the parent magma was mainly derived from a crustal magma source. The characteristics of trace element concentrations of cassiterite indicate skarn‐type affinities. The integrated evidence demonstrates that Sn enrichment initiated through syn‐exhumation decompression melting during crustal thickening, coupled with synkinematic asthenospheric upwelling. These synergistic processes established high‐temperature reducing conditions promoting biotite‐dehydration‐driven anatexis, liberating Sn into fractionated melts that underwent distal migration to generate concealed Sn‐mineralized granitic plutons, with subsequent ore precipitation localised within crustal‐scale fault systems through fluid–rock interaction. We propose that the Yunling Sn mineralization is temporally and genetically linked to ~20 Ma magmatism associated with regional shear zones. Consequently, concealed granitic intrusions and shear zone developed areas are potential targets for Sn prospecting in the Baoshan Block.