湘中白云铺铅锌矿床成矿物质来源及找矿方向

Ore-forming Material Sources and Ore Prospecting Direction of the Baiyunpu Pb-Zn Deposit in Central Hunan Province

以白云铺铅锌矿床为研究对象,对硫化物的硫、铅同位素组成特征进行分析,探讨成矿物质的来源。结果表明,黄铁矿、闪锌矿和方铅矿的δ^(34)S值变化范围大(-23.98‰^+23.20‰),具有不均一特征。黄铁矿、闪锌矿和方铅矿的δ^(34)S值不满足硫同位素分馏平衡条件下的大小关系,这可能与低温成矿有关。硫化物中较大的负δ^(34)S值,推断是由细菌还原赋矿地层中的海相硫酸盐所致,而较高的正δ^(34)S值可能是沉积盆地活动期间成矿流体在与富34S的海水蒸发岩发生相互作用的结果。方铅矿的铅同位素组成变化范围较小,组成相对均一,具有较高放射性成因的207Pb和208Pb。方铅矿的铅同位素数据在构造演化图的分布特征表明铅具有复杂来源的特征,原因可能是受到壳幔相互作用的影响,导致上地壳、下地壳和地幔物质可能都参与了成矿作用。矿区内主要发育白云石化、黄铁矿化和硅化。

Taking the Baiyunpu Pb-Zn deposit as the research object, the ore-forming materials sources were discussed by analyzing the characteristics of sulfur and lead isotope compositions of metal sulfides. The δ^34S values of pyrite, sphalerite and galena have a wide range between - 23.98‰ and ＋ 23.20‰ with the inhomogeneous characteristic. And they do not meet the relationship of relative size under the sulfur isotope equilibrium fractionation, which may be a result of the relatively low temperature mineralization. The higher negative δ^34S values of sulfides are probably resulted from the reduction of marine sulfate by bacteria. Moreover, the higher positive δ^34S values are possibly caused by the interaction between ore-forming fluid and ^34S-enriched seawater evaporates during the activity of sedimentary basin. The lead isotope compositions of galena have a limited range with the homogeneous feature and have the relatively high radiogenic ^207Pb and ^208Pb. According to the distribution characteristics in the tectonic model diagrams of lead isotope, they reflect a type of complex lead sources. Upper crust, lower crust and mantle are all probably involved in the mineralization because of the influence of crust-mantle interaction. The characteristics of sulfur and lead isotope geochemistry indicates the ore-forming materials of the deposit has complex sources. Pyritization and silicification are both related closely to the mineralization and are significant ore prospecting indicators.