湘南铜山岭铜多金属矿床成矿物质来源的S、Pb、C同位素约束

The Origin of Ore-Forming Material in the Tongshanling Cu-polymetallic Ore Field in Hunan Province:Constrains from S-Pb-C Isotopes

铜山岭铜多金属矿床是湘南W、Sn、Pb、Zn、Cu多金属矿集区的代表性矿床,本文对其不同类型岩石和矿石矿物进行了S、Pb、C同位素组成对比研究。矿石硫化物的δ34 S值变化范围为-1.9‰~5.7‰,平均值为2.6‰,硫主要来源于硫同位素组成均一化的岩浆。硫化物硫同位素平衡温度表明,矿床主要成矿温度为134~339℃。矿石铅的206 Pb/204 Pb、207 Pb/204 Pb、208 Pb/204 Pb比值分别为18.256~18.856、15.726~15.877、38.352~39.430;岩体岩石铅的206Pb/204Pb、207Pb/204Pb、208Pb/204Pb比值分别为18.617~18.805、15.721~15.786、38.923~39.073;两者铅同位素组成相同,都主要为上地壳铅,是由同一岩浆体系分异形成,可能来源于古老基底岩石。不同类型岩石、方解石矿物的δ13 CPDB值为-9.88‰~1.32‰,δ18 OSMOW值为11.67‰~17.68‰,从矽卡岩矿体到距岩体稍远的围岩地层,方解石矿物的δ13 CPDB、δ18 OSMOW值逐渐增大,成矿流体中的碳早期可能主要来源于岩浆,在成矿过程中有部分碳酸盐岩地层碳的加入。铜山岭矿床成矿物质主要来源于岩浆,赋矿地层对矿床成矿物质来源作用不显著,仅提供了少量成矿物质。

Tongshanling copper-polymetallic ore field is a typical W-Sn-Pb-Zu-Cu polymetallic deposit in south Hunan Province,China.This study carried on S-Pb-C isotopic anlaysis on various types of rocks and minerals.Theδ34S values vary from-1.9‰to 5.7‰ with the average value of 2.6‰,implying the main source of sulfur coming from the magma with homogeneous S isotopic composition.The equilibrium temperature of S isotopic shows the mineralization temperature is 134~339℃.The 206Pb/204 Pb,207Pb/204 Pb and 208Pb/204 Pb ratio values of ore rocks are 18.256~18.856,15.726~15.877 and 38.352~39.430,respectively;The 206Pb/204 Pb,207Pb/204 Pb and 208Pb/204 Pb ratio values of wall rocks are 18.617~18.805,15.721~15.786 and 38.923~39.073 respectively.The two types of rocks with consistent Pb composition of upper crust Pb indicatte that they originated from magma fractionation with an origin of ancient basement rock.Theδ13CPDBvalues of different types of rock and mineral calcite range from-9.88‰ to1.32‰;theδ18OSMOW values range from 11.67‰ to 17.68‰.Theδ18OSMOW andδ13CPDB values of calcite mineral increase gradually from the skarn rock to further wall rock,so the carbon in ore-forming minerals may generally come from magma,with some carbonate straitgraphic carbon involved later.The oreforming material in the Tongshanling ore fields mainly derived from magma,while the strata offer limited supply to the mineralization with small amounts of ore-forming material.