广西大厂铜坑锡多金属矿床成矿流体包裹体研究

铜坑锡多金属矿床是桂西北大厂矿田中的一个超大型矿床,由上部锡多金属矿体和深部新勘查发现的锌铜矿体组成。通过流体包裹体显微测温实验及热力学参数估算,对比研究了不同矿体成矿流体特征及其演化,探讨了流体沉淀机制。研究表明,锡多金属矿和锌铜矿均发育有H2O-NaCl-CO2型、H2O-NaCl型及纯CO2型包裹体,锡多金属矿成矿流体均一温度126.6~403.5℃(集中于260~360℃),盐度w(NaCleq)集中于4%~6%,密度0.234~0.967 g/cm3,pH为5.69~6.87;Eh为-0.4526~0.1814 V,fs2介于10-13.56~10-7.78,fo2介于10-32.53~10-24.11;锌铜矿成矿流体均一温度为138~432℃(集中于280~400℃);盐度w(NaCleq)集中于4%~9%;密度0.244~1.098 g/cm3;pH为5.79~7.17;Eh为-0.5903~0.1255 V;fs2介于10-10.86~10-6.34,fo2介于10-40.72~10-30.25。空间上由深部锌铜矿→上部锡多金属矿,成矿流体呈现温度降低、盐度降低、酸碱度降低、氧化还原电位升高、硫逸度降低、氧逸度升高的变化规律。流体沸腾、混合作用可能是锡石沉淀重要原因,富CO2流体沸腾作用可能是锌铜矿质沉淀重要原因。

Study on metallogenic fluid inclusions in Tongkeng tin polymetallic deposit, Dachang, Guangxi

Tongkeng tin polymetallic deposit is a superlarge ore deposit in Dachang ore field in northwest Guangxi,which is composed of upper tin polymetallic ore body and deep zinc and copper ore body discovered by new exploration.In this paper,the characteristics and evolution of ore-forming fluids of different ore bodies were compared,and the mechanisms of fluid precipitation were discussed by means of microscopic temperature measurements of fluid inclusion and thermodynamic parameter estimation.The results showed that both tin polymetallic ore and zinc-copper deposit had H2O-NaCl-CO2,H2O-NaCl and pure CO2 inclusions.The uniform temperature of the ore-forming fluid of tin polymetallic ore was 126.6~403.5℃(concentrated at 260~360℃),salinity w(NaCleq)concentrated at 4%~6%,density was 0.234~0.967 g/cm3,pH was 5.69~6.87;Eh was-0.4526~0.1814 V,fs2 was among 10-13.56~10-7.78,fo2 was 10-32.53~10-24.11;the homogenization temperature of zinc-copper ore-forming fluid was 138~432℃(concentrated at 280~400℃);salinity w(NaCleq)was concentrated at 4%~9%;density was 0.244~1.098 g/cm3;pH was 5.79~7.17;Eh was-0.5903~0.1255 V;fs2 was 10-10.86~10-6.34;fo2 was 10-40.72~10-30.25.Spatially,from deep zinc-copper deposits to upper tin polymetallic deposits,the ore-forming fluids showed changes in temperature,salinity,acidity and alkalinity,redox potential,sulfur fugacity and oxygen fugacity.Fluid boiling and mixing may be the important reasons for the precipitation of cassonite,and CO2-rich fluid boiling may be the important reasons for the precipitation of zinc-copper deposits.