西藏波龙斑岩铜金矿床成矿流体物理化学条件

STUDY ON THE FLUID INCLUSION PHYSICOCHEMICAL CONDITIONS OF BOLONG PORPHYRY COPPER-GOLD DEPOSIT IN TIBET

应用英国Linkam THNSG600型冷热台测试和前人的经验公式,对西藏波龙斑岩铜金矿床在岩浆晚期、磁铁矿-辉钼矿阶段、黄铜矿-黄铁矿阶段和硬石膏-黄铁矿阶段等4个成矿阶段利于主成矿元素Cu迁移的流体包裹体的一般特征及物理化学条件进行研究。研究结果表明,该矿床流体包裹体类型以含石盐和硫化物子矿物的三相包裹体为主,为高温(232~549℃)、低压(1.40×10~5~234.41×10~5Pa)、高盐度(NaCl质量分数28.65%~52.16%)、中—高密度(1.0683~1.1598g/cm^3)的流体;随着成矿进程的发展,各阶段流体逸度和活度均逐渐降低,pH值和Eh值逐渐升高,铜主要以Cu(H_2S)(HS)_2-形式存在,说明Cu在高温酸性流体中易成矿。

Using Linkam THNSG600 dating and calculating by experience formulas,this paper discusses the fluid inclusion characteristics of Bolong porthyry copper-gold deposit in Tibet,which is beneficial to the migration of the main ore-forming element Cu,and the metallogenic process includes four periods： magma-advanced stage,magnetite-molybdenite period,chalcopyrite-pyrite period and anhydrite-pyrite period. It shows that the type of fluid inclusion is mainly the threephases inclusion including Na Cl and metal sulfide daughter minerals. The ore-forming fluid forms in high temperature（ 232 ～ 549 ℃） and low pressure（ 1. 40 × 10^5～ 234. 41 × 10^5Pa）,with high salinity（ 28. 65 ～ 52. 16wt% Na Cl） and middle-high density（ 1. 0683 ～ 1. 1598 g / cm^3）. Along with the metallogenic process,the fluid fugacity and activity gradually reduce in each stages,while the values of p H and Eh increase. The element Cu mainly exits in the form of Cu（ H_2S）（ HS）_2～-,which shows that Cu is easier to mineralization in high tempreture and acidic fluids.