脉状黝铜矿型铜矿床的稳定同位素组成及其成因意义

Stable isotope compositions and their implications for ore genesis of vein tetrahedrite-type copper deposits

脉状黝铜矿型铜矿床是产于兰坪 思茅盆地中的一种新的铜矿床类型。碳酸盐及CO2 包裹体的δ13C值大多在 - 4‰～ - 7‰之间变化 ,显示碳来自地幔。矿石中铅同位素组成与盆地中喜马拉雅期碱性岩长石中铅的同位素组成一致 ,方解石和铁白云石的87Sr/86 Sr比值接近或稍高于碱性岩的87Sr/86 Sr的比值 ,显示矿石锶、铅与碱性岩锶、铅是同源的 ,均来自于上地幔。硫化物中硫的δ34S值大多集中在 0～ - 4‰之间 ,显示其硫主要是深部来源并有少量的地壳硫参与。包裹体水的δ18O和δD值显示成矿流体的水为大气降水、岩浆水和变质水的混合物。结合其它质、地球化学特征 ,笔者认为这类矿床的成因类型为壳 幔混合热液成因型。

A new type of copper deposits is discovered in the La n ping and Simao Basins.It is named after vein tetrahedrite type copper deposits. δ 13 C values for carbonate vein and CO 2 inclusions from the studied deposits range from-4‰ to -7 ‰,indicating mantle derived carbon.Pb isotopic compositions for sulfides fr om the studied ores are comparable to those for feldspar Pb from the Himalayan al kaline rocks and 87 Sr/ 86 Sr ratios for calcite and ankerite are simila r to or higher th an those for the Himalayan alkaline rocks,indicating mantle derived Sr and Pb.M ost of δ 34 S values for the sulfide from the studied ores range from 0 to-4‰,s h owing mantle derived sulfur mixed with crustal sulfur.δD and δ 18 O value s for w ater in fluid inclusions reveal that water in ore fluid are derived mainly from meteoric water,secondly,from magmatic water and metamorphic water.Combined with geolo gic geochemical features,this paper puts forward that the wein tetrahedrite ty pe copper deposits belong to mixed mantle crust hydrothermal genetic type of co pper deposits.