豫西龙门店银铅矿床铅硫同位素组成对成矿物质来源的示踪

Tracing indication of lead and sulfur isotope composition for the sources of ore-forming materials in Longmendian Lead-Silver Deposit in western Henan

龙门店银铅矿床位于华北克拉通南缘豫西熊耳山地体西段,是近年来新发现的构造蚀变岩型银铅矿床。通过对龙门店银铅矿床铅、硫同位素分析,获得该矿床主成矿阶段铅同位素^(206)Pb/^(204)Pb值为17.660~17.952,^(207)Pb/^(204)Pb值为15.388~15.566,^(208)Pb/^(204)Pb值为37.771~38.380,变化范围均不大,属于正常铅范围;硫同位素组成变化范围为-5.32‰~5.41‰,平均值-0.54‰。综合分析认为,矿石铅以幔源为主,具壳幔混合特征;硫主要来源地幔,并有地壳硫加入,具混合硫特征。铅、硫同位素组成表明,该矿床的成矿物质来源于造山过程中壳幔混合源,以幔源为主。

Longmendian Lead- Silver Deposit is located in the western part of Xiong＇ershan body on the southern margin of North China Craton. It is a tectonic altered rock type Lead- Silver deposit discovered in recent years. In order to find out the source of ore-forming materials,the paper studies the lead and sulfur isotopes in the main metallogenic stages. The results show that the Pb isotope ratio of ^（206）Pb/^（204）Pb is 17. 660 to 17. 952,the ratio of ^（207）Pb/^（204）Pb is15. 388 to 15. 566,the ratio of ^（208）Pb/^（204）Pb is 37. 771 to 38. 380,and the range of variation is normal without being too large. Sulfur isotopic compositions vary from- 5. 32 ‰ to 5. 41 ‰,and the average value is 0. 54 ‰. Comprehensive analysis thinks that the lead in the ore comes mainly from the mantle and is characterized by the mixture of mantle and crust; the sulfur comes mainly from the deep mantle and is mixed with crust sulfur. The sulfur and lead isotopic compositions of the ore deposit indicate that the source of ore-forming minerals is the mixed source from crust and mantle in the process of the orogenic process,with the mantle as the primary source.