The Geochemical Characteristics and Minerogenic Model for the Amo Hypothermal Tin Deposit in Ximeng County, Yunnan Province

Through studies on the element geochemistry, alteration of country rocks, ore-forming fluids and isotopegeochemistry of the Arno tin deposit in the metamorphic rocks of the Upper Proterozoic Ximeng Group, theauthors consider that the concentration of the B-F-Li-Rb-Cs-Sn association is related to acidic magmatism inthe study area. The Fe-Mg-Li tourmaline in the ore is the replaced product of the country rocks byhypothermal fluid. The δ^(18)O values of mineral separates are +2.01- +13.16‰ and their δ^(34)S values, +2.6-+7.2‰. The ore-forming materials were derived from hydrothermal fluid of granitic magma. For themineralization, the temperature is 450°-350℃, the pressure, 450-1000×10~5 Pa, and the age, Himalayan(21.5 Ma). According to the geochemical characteristics, a minerogenic model is established: the deposit is ahypothermal cassiterite-quartz vein type tin deposit controlled by the hidden Himalayan granites.

云南西盟阿莫锡矿成矿流体特征及矿床成因

对阿莫锡矿床成矿地质背景、矿床地质特征、成矿流体的成分、酸碱度、硫逸度等物理化学条件的分析研究表明,阿莫锡矿床主要赋存于西盟群永龙组下段片岩和大黑山组上段变粒岩中,有明显的层控性质;成矿物质主要来源于隐伏花岗岩体;成矿流体由弱碱性向弱酸性演化,并经历了迁移、沸腾、沉淀的过程,显示多组分、高盐度、高矿化剂等特征。主要成矿阶段包裹体均一温度集中于380～430℃之间,成矿深度约3.9km,流体密度为0.89～0.98g/cm3,流体盐度35%,矿床成因类型属于高温气成热液锡矿床。

云南西盟锡矿阿莫矿段控矿条件

锡矿体产于蚀变片岩中,矿床形成严格受有利地层岩性、构造和蚀变等地质条件的控制,矿床应属岩浆期后气成高温热液矿床。