广西佛子冲铅锌矿田成因刍议

DISCUSSION ON THE GENESIS OF FOZICHONG LEAD-ZINC ORE FIELD

广西佛子冲铅锌矿田有两种不同的矿化类型 ,一种以浅色闪锌矿为标志 ,矿体呈层状、似层状产出 ,产状与地层一致 ,矿石具典型的同生构造 ,代表了成矿第一世代 ;另一种以铁闪锌矿为标志 ,矿体呈似层状、脉状及不规则状等 ,靠近岩体接触带或断裂与赋矿层的交汇部位产出 ,代表了成矿第二世代。矿田层状矽卡岩与接触交代型矽卡岩明显不同 ,其化学成分特征与现代海洋热水沉积物十分相似 ,推断是一种特殊类型的喷流岩。矿物流体包裹体成分反映了两种不同性质热液的活动 ,氢、氧同位素组成所指示的成矿热水以大气水或地下热卤水为主。佛子冲矿田的形成经历了志留纪海底喷流—沉积成矿和燕山期与岩浆活动有关的热液迭生—改造成矿两个不同时期的成矿事件 ,在早期矿化基础上经多次、多成因成矿事件复合而成。

There are two different kinds of ore in Fozichong Pb-Zn ore field, Leucocratic sphalerite is the guide mineral in the first ore type which has syngenetic structure and represents the first generation of mineralization. Marmatite is the guide mineral of the second ore type which appears in bedded , veined and irregular ore bodies near contact zone of magmatic rock or joint positions between faults and ore beds. Bedded skarn in the ore field is different from contact-metasomatic skarn , its chemical composition is similar to the present marine hot-water sediment , such skarn is a special kind of exhalative rock. Fluid inclusion composition shows two different hot-water's activity.Hydrogen and oxygen isotope composition of water in fluid inclusions indicates that ore- bearing hydrothermal solution origined mainly from atmospheric water or deep connate water.The forming of ore field experienced two periods of mineralization , one was seafloor -exhalative sedimentary mineralization in Silurian period,another was hydrothermal telescoping-transforming mineralization related to magma activity in Yenchan period. The main mechanism of polygenetic mineralization in the same position was the inheriting locatlon of many mineralization incidents on the condition of induced action of ore bodies formed in early generation.