新疆包古图斑岩铜矿伴生元素金和银赋存状态初步研究

新疆西准噶尔包古图斑岩铜矿床Au平均含量0.25g/t,Ag为2.56g/t,Cu为0.30%,属于富金斑岩铜矿。伴生金和银矿化作用有两期:早期为斑岩矿化,形成了Cu-Mo-Au矿化组合,是主矿化期;后期叠加了Cu-Au-Ag-Te-Bi矿化,规模不大,出露于矿床的局部部位,但对矿石起到了加富作用。通过对钻孔薄片和光薄片的镜下观察及电子探针成分分析,认为早期矿化中Au和Ag主要呈固溶体形式存在于硫化物中,分布比较均匀,基本上不出现独立矿物,Au含量明显高于Ag;晚期矿化形成了复杂的Cu-Au-Ag-Te-Bi矿物,矿石呈浸染状和脉状叠加在早期矿化之上,以银矿物为主,与多种碲铋类矿物共生,主要银矿物有碲银矿、铋-碲银矿(?)、银-辉碲铋矿(?)、银-硫铋铜矿、银金矿等。晚期矿化规模不大,但对于提高矿床的经济价值具有重要意义。

A preliminary study of the modes of occurrence of associated Au and Ag in the Baogutu porphyry copper deposit, Xinjiang Autonomous Region, China

The Baogutu porphyry copper deposit,a gold-rich porphyry copper deposit,is located on the margin of western Junggar Basin in Xinjiang.The average Au,Ag and Cu contents of the deposit are 0.25 g/t,2.56 g/t and 0.30%,respectively.Two ore-forming stages have been observed.The early stage,during which Cu-Mo-Au assembly was formed,seems to have been the main mineralization stage.The late stage,during which the Cu-Au-Ag-Te-Bi assembly was generated,only occurred in local places of the ore deposit and was not large in scale,but it played the role of enriching the ore.According to the microscope observation and electron microprobe analyses of the polished sections and polished thin sections,the authors consider that at the early ore-forming stage,Au content was higher than Ag content,and these two elements existed homogeneously in sulfides as solid solutions,with no independent minerals formed.The late ore-forming stage was characterized mainly by the formation of argentiferous minerals and complex Cu-Au-Ag-Te-Bi minerals,with the major minerals being hessite,Bi-bearing hessite(?),Ag-bearing tetradymite(?),Ag-bearing wittichenite,electrum etc.These min-erals are present as slender veins superimposed upon earlier mineralization.Though limited in scale,the late stage mineralization played an important role in improving the economic value of the deposit.