Objective The Dechang−Huili region, located in the Yangtze Plate and part of the middle section of the Kangdian Foreland Uplift Belt, has experienced multiple tectonic−magmatic events.

Methods This study takes Chahe tin deposit and Tongchangpo Cu−Sn−Fe deposit as the research objects, conducts systematic sampling, and carries out cassiterite U−Pb dating, cassiterite trace element analysis, and sulfide S isotope testing.

Results The LA−ICP−MS U−Pb dating of Tongchangpo's cassiterite is 841±11 Ma, linking to the Neoproterozoic subduction−collision event on the Yangtze Block's western margin. The δ³⁴S of sulfides in Chahe tin deposit ranges from +14.70‰ to +22.30‰. Tongchangpo cassiterite is rich in Zr, Hf, Nb and Ta. Mosuoying Pluton with strong crystallization differentiation and low oxygen fugacity is the material source of tin deposits, while Huili Group slightly metamorphic rocks are the main sulfur source. Ore−forming hydrothermal fluids are medium−high temperature and slightly reducing. During the Neoproterozoic subduction−collision event in the western margin of the Yangtze Block, partial melting of the Paleo−Mesoproterozoic metamorphic sedimentary crust formed magmas rich in halogen elements (B, F, etc.). In a low oxygen fugacity environment, these magmas formed stable complexes with halogens during long−distance migration, eventually leading to cassiterite mineralization. Meanwhile, ore−bearing hydrothermal fluids underwent metasomatic reactions with wall rocks, forming pyritization in structural weak zones. The prospecting criteria for tin polymetallic deposits in the Huili−Dechang area can be summarized as follows: ①Metamorphic clastic rocks and carbonate rocks; ②Jinningian highly differentiated S−type granite (Mosuoying Pluton); ③Interlayer fracture zones in the contact zone between the Mosuoying Pluton and the surrounding rocks.

Conclusions Combining previous data and the results of this study, the Huoyaopo, Tongchangpo and Wannianpo areas meet the prospecting criteria. They feature high concentration and wide distribution of tin anomalies, and ore bodies have been delineated through trench verification, showing great prospecting potential.