Classification and type association of tin deposits in Southeast Yunnan Tin Belt

Abstract

Pneumato-hypothermal to meso-epithermal tin-polymetallic (W, Be, Bi, Mo, Cu, Pb, Zn and Ag) deposits, dominated by cassiterite-sulfide type and cassiterite-quartz type, are extensively developed around granite intrusives in the Southeast Yunnan Tin Belt genetically related to Yenshanian tecto-magmatism. The deposits are grouped into two classes, four associations and fourteen types according to the classification scheme proposed by the author to reflect their geological and genetic characteristics as well as economic implications. The deposits are arranged in an apparent zonal pattern from the granite body outwards in terms of “association” (cassiterite-feldspar → cassiterite-quartz → cassiterite sulfide), typical ore-forming metals (Sn-W-Be-Mo-Nb-Ta-Tr → SnW-Cu-In → Sn-Pb-Zn-As-Cd), and formation conditions (pneumato-hypothermal → hypothermalmesothermal → mesothermal-epithermal), although such distribution pattern may be more or less complicated by local specialities of granite petrochemistry, host rock lithology and structure.