贵州天柱云洞铅锌矿床地质地球化学特征

Geological and geochemical characteristics of the Yundong Pb-Zn deposit,Tianzhu County,Guizhou Province,China

本文从矿物学特征、稀土元素、硫同位素地球化学特征与区内铅锌成矿的关系,探讨铅锌矿成矿物质来源,以及震旦系铅锌成矿规律。结果表明,铅锌矿容矿围岩主要为碳酸盐岩,矿物以闪锌矿(米黄色)和黄铁矿为主,矿石结构以为细晶粒状为主,矿石构造以角砾状、脉状交代、细粒浸染状为主。铅锌矿化岩石中Pb、Zn、Ag、Cd含量富集。矿石和围岩的∑REE分别为9.8×10^-6~93.1×10^-6和10.2×10^-6~127×10^-6,二者较为接近,表现为轻稀土富集、重稀土亏损的特征。硫同位素组成为δ34S在13.5‰~25.3‰之间,明显低于早寒武世海水的的硫同位素组成(δ34SVCDT=29.00‰~37.2‰),均值32.6‰±1.8‰,比大河边重晶石矿床中的重晶石的硫同位素组成(δ34SBrt=37.5‰~45‰)更低,与湖南董家河铅锌矿床硫化物的硫同位素组成比较接近,认为硫来源于震旦纪陡山沱期古海水硫酸盐的还原作用。

Based on the relationship between characteristics of mineralogy,trace and rare earth elemental,sulfur isotopic geochemistries and the lead-zinc mineralization of the deposit,in this paper,we have discussed the source of lead-zinc oreforming minerals and metallogenic regularity of the Sinian lead-zinc deposit.The ore-hosting rock of Yundong lead-zinc deposit is mainly carbonate rock.The sulfide minerals are mainly sphalerite(beige)and pyrite.The ores have mainly fine grained texture and brecciated,veining,and fine-grained disseminated structures.Pb,Zn,Ag,and Cd are enriched in lead-zinc mineralized rocks.The ores and wallrocks contain∑REE contents of 9.8×10^-6-93.1×10^-6 and 10.2×10^-6-127×10^-6,respectively,with similar REE distribution patterns which are mainly characterized by the enrichment of light rare earth elements and the depletion of heavy rare earth elements.The sulfur isotopic compositions(δ34S)vary from13.5‰to 25.3‰,with an average value of 32.6‰±1.8‰.They are significantly lower than the sulfur isotopic composition of Early Cambrian seawater(δ34SVCDT=29.00‰-37.2‰),even much lower than sulfur isotopic compositions of barites in the Dahebian barite deposit(δ34SBrt=37.5‰-45‰),but are relatively close to those of sulfides in the Dongjiahe lead-zinc deposit in Hunan Province.Therefore,it is believed that the sulfur of the deposit could be originated from the reduction of sulfates in paleo-seawater in Sinian Doushantuo period.