滇西北羊拉铜矿床3175m中段铜矿石和构造岩地球化学特征及地质意义

羊拉铜矿床是金沙江缝合带内的典型代表性铜矿床,其矿体呈层状、似层状、脉状及透镜体状产出,且明显受断裂构造及层间破碎带控制。采用电感耦合等离子体质谱仪(ICP-MS)分析技术重点对羊拉矿床里农矿段深部3175 m中段铜矿石和断裂构造岩进行主量和微量-稀土元素组成研究。结果表明,铜矿石和各构造岩均富集CaO、Al₂O₃与TFe₂O₃;羊拉矿床NW向断裂可能与铜成矿作用无关。此外,断裂构造岩微量元素R型聚类分析和因子分析表明存在5个微量元素组合:1)围岩微量元素组合(Ba、Rb、REE、Th、Li、U、Be、Ga、Cs、Cr、Ta、V、Sc、Hf、Zr、Nb);2)地质意义不明元素(Sr);3)铜矿化中温成矿元素组合(Cu、Bi、Co、Ge);4)铅锌矿化中低温成矿元素组合(Zn、Cd、Pb、Ag、In、Sn、Ni、Tl)和5)高温成矿元素组合(Mo、W);表明羊拉矿床铜形成于高中低温各热液成矿阶段的成矿温度环境。稀土元素组成特征指示铜成矿作用可能主要与NE向断裂、近EW向断裂构造活动有关,而大理岩和绢云砂质板岩对成矿作用贡献较小。上述铜矿石和构造岩地球化学特征可为下一步该矿床找矿勘查提供理论指导。

Geochemical characteristics of copper ore and tectonite in the underground tunnel 3 175 m section from the Yangla Copper deposit in northwest Yunnan and their geological implications

The Yangla copper deposit is a representative deposit in Jinshajiang suture zone.Its ore bodies are layered,vein-like and lenticular,and obviously controlled by structures and interlayer fracture zones.In this paper,Inductively Coupled Plasma Mass Spectrometry(ICP-MS)analytical technology was used to measure the major and trace-rare earth element compositions of copper ore and tectonite in the underground tunnel 3175 m section of the Linong ore block,Yangla copper deposit.The results showed that copper ore and various tectonites were enriched in CaO,Al₂O₃,and TFe₂O₃.The NW-trending fault of Yangla copper deposit may not be related to the copper mineralization.Furthermore,R-type cluster analysis and factor analysis showed that there were five trace element assemblages in tectonites:1)Assemblage of trace elements in wall-rock(Ba,Rb,REE,Th,Li,U,Be,Ga,Cs,Cr,Ta,V,Sc,Hf,Zr,and Nb);2)Geologically significance unknown trace element assemblage(Sr);3)Mesothermal metallogenic trace element assemblage(Cu,Bi,Co,and Ge);4)The moderate-low temperature metallogenic trace element assemblage(Zn,Cd,Pb,Ag,In,Sn,Ni,and Tl);5)The high-temperature metallogenic trace element assemblage(Mo and W).The above findings indicated that the copper of Yangla deposit was formed in various hydrothermal mineralization stages from high-medium-low temperature environments.The composition characteristics of rare earth elements indicated that copper mineralization may be mainly related to NE-trending faults and near-EW-trending faults,while the marble and sericite slate had less contribution to the copper mineralization in the Yangla copper deposit.The above-mentioned geochemical characteristics of copper ore and tectonite can provide theoretical guidance for further mineral exploration in the Yangla copper deposit.