广西东桃铅锌矿床流体包裹体研究

FLUID INCLUSION OF DONGTAO LEAD-ZINC DEPOSIT IN GUANGXI

广西东桃铅锌矿床流体包裹体类型主要有单相盐水溶液包裹体 ( LH2 O) ,气液两相盐水溶液包裹体 ( LH2 O+VH2 O)和单相气体包裹体 ( VH2 O) 3类 ;结合矿床地质特征 ,根据流体包裹体均一温度可将成矿作用分为 3个阶段 :1层状—条带状矽卡岩化铅锌矿成矿阶段 ;2似层状—浸染状绿帘石化铅锌矿成矿阶段 ;3脉状碳酸盐化铅锌矿成矿阶段。测得均一温度范围为 90～3 5 5°C,最佳成矿温度为 2 0 5～ 2 60°C,属中低温矿床 ,为矿区的主要成矿阶段 ;根据流体包裹体的盐度、均一温度资料获得矿化深度为 0 .66～ 1.2 0 km,成矿流体的盐度 w( Na Cl)为 7.2 %～ 16.5 %,成矿流体成分具有 w( Na+ ) >w( K+ )、w( Cl-) >w( F-)的特征。低盐度的 Na Cl-H2 O体系 ,可能主要来源于古海水。矿石铅同位素组成反映其物质来源主要为壳源 ,而矿石硫同位素值 [δ( 3 4 S)为-6.3‰～ -2 .9‰

The systematical study of Dongtao lead-zinc deposit shows that fluid inclusions in minerals of orefield include three types:single-phase liquid inclusions(L_(H_2O)),double-phase liquid-vapor inclusions(L_(H_2O)+V_(H_2O)) and single-phase vapor inclusions(V_(H_2O)).Determination of homogenization temperatures of fluid inclusions indicates that the deposit is a low-to-moderate one with metallogenetic temperatures ranging from 90 to 355°C(usually 205-260°C), and its mineralization can be subdivided into three stages:①stratified-banded skarn lead-zinc deposit metallogenic stage,②stratoid-disseminated epidotization lead-zinc deposit metallogenic stage,③veined carbonate lead-zinc deposit metallogenic stage. Projection of salinities and homogenization temperatures shows that the mineralization depth of the deposit is 0.66-1.20 km with the salinity ranging from 7.2%-16.5%.Component analyses of the fluid inclusions indicate that the metallogenetic fluid is rich in Na^+ and poor in K^+,belonging to low-salinity NaCl-H_2O system and might be mainly derived from paleo-sea-water. Components of lead isotopes reflect that the metallogenetic materials mainly come from the crust while the δ(^(34)S) values(-6.3‰～-2.9‰)of ores indicate that sulfur is mainly from sulphate and bioaccumulation.