川滇黔矿集区天宝山铅锌矿床硫化物原位硫同位素特征

In-situ sulfur isotope characteristics of sulfides from Tianbaoshan lead-zinc deposit, Sichuan-Yunnan-Guizhou metallogenic Province

川滇黔铅锌矿集区是中国最重要的铅锌矿产地之一,文章以该矿集区内四川天宝山大型铅锌矿床为例,开展了LA-MC-ICP-MS硫化物原位硫同位素与LA-ICP-MS闪锌矿原位微量元素分析,为认识该类矿床硫源和矿床成因提供地质地球化学依据。微量元素数据计算所得成矿温度在130~170℃之间,是典型MVT型矿床的成矿温度。LA-MC-ICP-MS硫化物原位硫同位素分析得到的该矿床硫化物的δ;S值在+3.3‰~+12.0‰,在样品尺度上测量值之间的δ;S值变化可达4.5‰,远高于分析方法的精度(±1.2‰),此次测量值比前人用全岩粉末测得的δ;S值(+3.3‰~+4.8‰)偏大,成矿物质硫应为赋矿地层中的硫酸盐通过热化学还原作用生成,且是在原位还原的。此外,纵观不同产出位置硫化物的δ;S值发现,从矿床深部到浅部(海拔1900~2300 m),矿体产状没有显著变化,硫化物的δ;S值逐渐变大,反映了从低到高逐渐靠近成矿热液中心的趋势。综上所述,天宝山铅锌矿床属于MVT型铅锌矿。

Sichuan-Yunnan-Guizhou (SYG) Lead-zinc metallogenic province is one of the most important lead-zinc mining areas in China.Taking the Tianbaoshan large Pb-Zn deposit in Sichuan Province as an example,LA-MC-ICP-MS in-situ sulfur isotope analysis of sulfide and LA-ICP-MS in-situ trace element analysis of sphalerite were combined to provide a geological and geochemical basis for understanding the sulfur source and genesis of the de‐posit.The mineralization temperature calculated by using the trace element data is between 130℃and 170℃,which belongs to mineralization temperature of typical MVT deposit system.Theδ;S values of sulfides in the de‐posit obtained by LA-MC-ICP-MS in-situ sulfur isotope analysis range from+3.3‰to+12.0‰.Theδ;S values of sulfides measured on the sample scale vary up to 4.5‰,which is far higher than the accuracy of the analytical method (±1.2‰).The values ofδ;S measured in this study is larger than the previous published values ofδ;S measured with whole rock powder (+3.3‰~+4.8‰),indicating that the ore-forming sulfurs are generated by ther‐mochemical reduction of sulfates in ore-bearing strata,and the sulfates are reduced in situ.As soon as the reduced sulfurs were generated,they reacted with metal ions in ore-forming fluid quickly and resulted in sulfide precipita‐tion.In addition,from the depth of the deposit to the shallow part (altitude 1900~2300 m),there is no significant change in the occurrence of the ore body,while theδ;S value of the sulfide gradually increases from+3.3‰to+12‰,reflecting the trend vertically from low to high that the sulfides are gradually close to the metallogenic hy‐drothermal center.In conclusion,the Tianbaoshan Lead-zinc deposit belongs to MVT type lead-zinc deposits.