Geological Characteristics And Metallogenesis Of Siguangping Tin Deposit,western Yunnan

Siguangping tin deposit is one of Lailishan tin deposit,occurred in the southeast of the Lailishan granite,controlled by F₆ and F₁₅.This paper has conductedstudy on the Siguangping tin deposit based on the ore deposit geochemistry,ore-forming fluid,metallogenetic age and tectonic background,in order to identify the ore deposit types,discusses the metallogenic material source and metallogenic dynamics background.The main ore minerals of Siguangping tin deposit are pyrite,pyrrhotite,magnetite,cassiterite,arenopyrite etc.Gangue minerals are quartz and calcite.Ore structure are massive structure,banding structure.Ore texture are granular texture,cataclastic texture,mortar texture,metasomatic texture.The main ore stage is hydrothermal stage,divided 3 metallogenic phases,including pyrrhotite?pyrite?phase,quartz-sulfide phase and pyrite calcite phase.The outcome of the pyrite and cassiterite by EMPA indicated that three metallogenic stages of pyrite S/Fe ratio of less than 2,with sulfur loss.The Co/Ni ratios are mostly located into volcanic origin area.The wFe/w?As+S?ratio of 0.823?0.910,instructing that the pyrite formed in hypabyssal environment.The content of FeO and Ta₂O₅ are relatively higher in cassiterites,instructing that the cassiterites sedmented in weak acid.The ore-forming temperature of Siguangping tin deposit is between 110?260?.Ore-forming fluid has the features of low temperature and low salinity and low density.Sulfur isotope?³⁴S value shows the source of magma sulfur.Ore-forming fluid derived from the mixture of magmatic water and atmospheric precipitation.The deposit is medium-low temperature cassiterite sulphide hydrothermal deposit.The metallogenic age of Siguangping tin deposit is 46.0Ma,the metallogenic age of Laoxiongwo tin deposit is 49.8Ma.The two ages both are closely,illustrating a close relationship between tin mineralization and early Himalayan magmatism.The stability of Sn⁴⁺is reduced because of the fluid property transform into acidity,reduce temperature and pressure,increase oxygen fugacity.Those changes lead Sn deposited.