陕西略阳陈家坝铜铅锌多金属矿床硫化物微量元素和硫同位素地球化学特征

Geochemical Characteristics of Trace Elements and Sulfur Isotopes of Sulfides from the Chenjiaba Cu-Pb-Zn Polymetallic Deposit,Lveyang County,Shaanxi Province

为探讨勉-略-阳矿集区陈家坝铜铅锌多金属矿床的成矿物质来源及矿床成因,以矿床中的黄铁矿、黄铜矿和闪锌矿为研究对象,采用电感耦合等离子体质谱仪和同位素质谱仪分析方法,开展了稀土元素、微量元素及S同位素地球化学研究。结果表明,与大陆上部地壳微量元素丰度相比,黄铁矿中Cu、Pb、Zn、Ag、Au等成矿元素富集,可能反映了成矿流体中富集成矿元素;黄铁矿的Y/Ho=5.5-42.0,与石英角斑岩的Y/Ho值基本一致,指示岩浆流体参与成矿;黄铁矿的Co含量为54.8×10^-6-165.02×10^-6,Co/Ni值为1.29-5.95,显示该矿床形成于中低温环境,其经历了早期火山喷流成矿和后期热液成矿作用;硫化物的δ34S值为4.88‰-8.90‰,硫源由卤水硫酸盐与海水硫酸盐混合组成。

In order to explore the source of ore-forming materials and the genesis of the Chenjiaba Cu-Pb-Zn polymetallic deposit in the Mian-Lve-Yang ore-concentrated district,a geochemical study on REE,trace elements,and S isotopes of pyrite,chalcopyrite and sphalerite of the deposit has been carried out by using the ICP-MS and EA-IRMS instruments in this paper. The results show that the ore-forming elements,such as Cu,Pb,Zn,Ag,and Au etc. in pyrite are enriched comparing with the abundances of trace elements in the upper crust of the earth. It might reflect that the ore-forming elements were enriched in the ore-forming fluid. The Y/Ho ratios of pyrite（ varying from 5. 5 to 42） are similar to those of the quartz keratophyre,indicating the involvement of magmatic hydrothermal fluid in the mineralization. In addition,the pyrite has Co contents of 54. 8×10^-6—165. 02×10^-6 and Co/Ni ratios ranging from 1. 29 to 5. 95,indicating that the deposit was formed in a medium to low temperature environment by the early volcanic exhalative mineralization and late hydrothermal mineralization. Sulfur isotopes of sulfides vary from 4. 88‰ to 8. 90‰,indicating that sulfur could be sourced from the mixture of the brine sulfate and sea water sulfate.