西藏甲玛铜多金属矿床角岩岩石类型、成因意义及隐伏斑岩岩体定位预测  

Rock types and genetic significance of hornfels and location prediction of concealed porphyry bodies in Jiama copper polymetallic deposit,Tibet

作　　者：王崴平[1] 唐菊兴[2] 

机构地区：[1]中国地质科学院研究生部,北京100037 [2]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037

出　　处：《矿床地质》2011年第6期1017-1038,共22页Mineral Deposits

基　　金：危机矿山接替资源找矿专项典型矿床及成矿规律总结研究项目(编号:20089932);国家973项目(编号:2011CB403103);青藏专项(编号:1212010012005)共同资助

摘　　要：甲玛铜多金属矿床中发育角岩，按角岩与成矿的关系，可将其划分为成矿前角岩与成矿期角岩，多属钠长绿帘角岩相，矿物共生组合主要为钠长石＋黑云母＋石英。成矿前角岩以细晶化为主要特征，大多斑晶矿物没有独立晶形，其岩性主要为原生黑云母角岩（具典型斑点状、条带状构造）、长英质角岩；成矿期角岩的热液斑晶矿物具独立晶形，其岩性主要为硅化角岩、热液黑云母一绿泥石角岩等。参照地层接触关系、岩石组构特征，通过岩石化学和地球化学特征进行综合对比，确定了角岩的原岩为林布宗组砂板岩和碳质板岩。角岩是热变质作用的产物，在这一前提下，笔者统计了0～40勘探线各钻孔角岩与角岩型矿体厚度等值线图，与各钻孔角岩内Cu、Mo元素丰度浓集中心综合对比，并结合最新的地质勘探发现，对隐伏斑岩岩体进行了平面定位，并构建了甲玛铜多金属矿床模型，还原了甲玛矿区的成矿作用序列，对比阐释了热变质作用与热液蚀变作用对角岩型矿化的意义。The hornfels thermal metamorphism is well developed in the Jiama copper polymetallic deposit. Rock types of hornfels can be divided into the pre-oreforming stage hornfels and the syn-oreforming ones, belonging to AEH facies with the main mineral association being albite ＋ biotite ＋ quartz. The pre-orefoming hornfels consists of protogenie biotite hornfels with typical mottled and banded structures, and felsic hornfels characterized by re- fined grains, with most phenocryst minerals having no independent morphology. The syn-oreforming hornfels silicified hornfels and hydrothermal biotite-chlorite hornfels, with phenocryst minerals possessing good crystal habit. Based on stratigraphic contact relationship and rock fabrics, the authors infer that the protoliths of horn- fels were sandy slates and carbonaceous slates, evidenced by comparative study of petrochemical and geochemical features. Considering that hornfels is a natural tracer material for thermal metamorphism, the authors contoured the thickness of hornfels and related mineralization and located the concentration centers of Cu and Mo, which helps indicate the location of the concealed porphyry body with the help of the la- test exploration results. The authors built a model for the Jiama copper polymetallic deposit, which indicates the sequence of mineralization in the ore deposit and comparatively explains the roles of the thermal metamorphism and hydrothermal alteration in hornfels type mineralization.

关 键 词：地质学 角岩 成矿前角岩 成矿期角岩 热变质 隐伏斑岩岩体 矿床模型 斑岩成矿系统 演化 甲玛 

分 类 号：P618.41[天文地球—矿床学]