简论中国层控铜铅锌矿床的稳定同位素地球化学特征

STABLE ISOTOPIC CHARACTERISTICS OF COPPER, LEAD AND ZINC STRATABOUND ORE DEPOSITS IN CHINA

层控矿床是构造运动、岩浆活动和沉积作用的综合产物，按其大地构造环境和沉积建造可划分为４大类、１３个亚类。层控矿床的稳定同位素组成按这一分类呈明显的规律性。不同建造中硫化物的硫同位素组成与其来源有关，并随后期叠加改造作用的增强而趋于均一。铅同位素组成反映了时代由老变新，由正常铅－混合铅－异常铅的演化规律，μ值也有增大的趋势，由幔源铅逐渐向壳幔混合型过渡。其含矿流体氢、氧同位素组成为建造水，显示了岩浆水与大气降水的混合，在不同建造类型中存在着较大差异，并随后期叠加改造作用的增强向混合含矿流体方向演化。总之，层控矿床的稳定同位素组成，其背景值反映了原始沉积环境，并明显地受沉积建造类型控制，后期叠加改造作用也可造成同位素组成的不同程度的变化。

he stratabound ore deposits are mainly the results of tectonisms, magmatisms and sedimentations. They can be devided into four types containing thirteen subtypes according to their tectonic settings and sedimentary formations. With this classsification,the stable isotopic composition of stratabound ore deposits is found to have been in a regular distribution. Sulfur isotopic composition of sulfide in different formations was related to their source, and tended to be uniform with the growing stacked reworking at later stages. Lead isotopic composition which evoluted from normal lead through mixed lead to anomalous lead with time passing,transformed from mantle-derived lead to mantle-crust-derived lead which was indicated by the growing μ value.Hydrogen and oxygen isotopic composition of ore-bearing fluid was of formation water. It varied greatly with different formation types and evoluted to mixed ore-bearing fluid with the growing of stacked reworking at later stages. The background values of stable isotopic composition of stratabound ore deposits indicate the original sedimentary environment and are obviously controlled by the formation types. In the meanwhile, the stacked reworking at later stages would also bring out the change of isotopic composition to a considerable extent.