| Abstract:Based on the fluid inclusion studies, this paper discusses tentatively the physical-chemical conditions and material sources for mineralization of the Yinyan porphyry tin deposit, with the main understanding summarized as follows: 1．The minerals in the porphyry tin ore contain lots of high-salinity fluid inclusions and CO2-rich inclusions. It has been determined that the ore-forming fluids had salinity as high as 40-64 wt％NaCl, temperature from 300℃ to 460℃, pressure about 100 bar, fO2 10-25 bar, fCO2 101.1 bar, and Eh about 0.8, so porphyry tin mineralization must have taken place under the condition of weak reduction and boiling of ore—forming fluids caused by decreasing pressure．2．Minerals in the veinlike tin ore contain only a few liquid inclusions. The ore-forming fluids had low salinity of 2-7 wt％ NaCl, temperature from 260℃ to 320℃, pressure some 300 bar, fO2 10-21 bar, fCO2 100.27 bar, and Eh about 0.8．It is therefore considered that this sort of tin ore must have formed during the decrease in temperature and salinity of the ore—forn-ing fluids. 3．The hydrogen and oxygen isotope data of the inclusions suggest that the metallogenic fluids forming the porphyry tin deposit mostly came from the magma, and that during the formation of veinlike ore, magrnatic water was mixed with rain． |
