新疆维宝矽卡岩铜铅锌矿床维西矿段矿物学特征  

Mineralogical Characteristics of the Weixi Ore Block in the Weibao Skarn-type Copper-Lead-Zinc Deposit,Xinjiang

作　　者：钟世华[1] 丰成友[1] 李大新[1] 赵一鸣[1] 任雅琼[1] 周建厚[1] 刘建楠[1] 王辉[1] 于淼[1] 

机构地区：[1]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：《地质学报》2017年第5期1066-1082,共17页Acta Geologica Sinica

基　　金：国土资源部公益性行业科研专项经费项目(编号201411025);中国地质调查局地质调查项目(编号1212011085528;12120113093600);中国地质调查局高层次地质人才培养计划(编号201309)和青年地质英才计划(编号201112)资助的成果

摘　　要：维宝矽卡岩铜铅锌矿床位于新疆与青海两省交界处,大地构造位置属祁漫塔格造山带东段,可以分为维东、主矿段和维西三个矿段。主矿段和维东矿段以铅锌矿化为主,铜矿化很少,而维西矿段铜、铅、锌矿化均较发育。本次我们选取维西矿段的矽卡岩和矿石样品,进行了详细的矿物学研究。根据矿物共生组合、矿石组构以及脉体的穿插关系,可以将维西矿段成矿过程分为4个阶段,即早期矽卡岩阶段、晚期矽卡岩阶段、石英-硫化物阶段和石英-碳酸盐阶段,其中石英-硫化物阶段是主要的成矿阶段。矽卡岩矿物主要为石榴子石、辉石、绿帘石和角闪石等,硫化物主要为黄铜矿、方铅矿、闪锌矿、黄铁矿和磁黄铁矿等。电子探针分析表明,石榴子石成分以钙铁榴石分子(And=59.00%～97.70%)和钙铝榴石分子(Gro=1.92%～40.42%)为主,为钙铁—钙铝系列石榴子石;辉石主要由透辉石分子(Di=45%～91%)和钙铁辉石分子(Hd=8%～53%)组成,表现在矿物上以透辉石为主,而钙铁辉石数量很少;角闪石成分变化范围比较大,但总体上为透闪石—阳起石系列。综合矿物组合和化学成分特征表明维宝矿床维西矿段矽卡岩为钙矽卡岩。此外,具有环带结构的石榴子石从核部到边部,化学成分表现出有规律的变化,Al2O3含量先上升后下降,FeOT含量则先下降后上升。这表明随着交代作用的进行,成矿流体的pH值不断发生变化,由最初的弱酸性—碱性条件转变为近中性条件,最终又恢复到弱酸性—碱性条件。维西矿段硫化物的金属原子与硫原子的比值大部分都大于理论值,表明它们形成于硫逸度较高的环境。此外,闪锌矿中Fe、Zn含量变化范围比较大,Zn=54.50%～64.75%,Fe=1.15%～10.16%,这种大范围变化指示成矿过程中温度和硫逸度可能发生波动。The Weibao skarn-type Cu-Zn-Pb polymetallic deposit, located at the junction of Xinjiang and Qinghai, tectonically belongs to the eastern part of the Qimantagh orogen. It comprises three ore blocks, referred to as Weidong, Main and Weixi respectively. The Weidong block is characterized by abundant Pb- Zn mineralization and minor Cu mineralization, while the Weixi block is characterized by abundant Cu-Pb- Zn mineralization. In this study, we carried out detailed research on the mineralogy of the skarn and ore samples from the Weixi block. On the basis of the mineral assemblages, ore structures and crosscutting relationship, the ore-forming process of the Weibao deposit can be preliminarily divided into four stages, i. e. , the early skarn stage, the late skarn stage, the quartz-sulfide stage and the quartz-carbonate stage, with the quartz-sulfide stage being the main ore-forming stage. Skarn minerals are mainly composed of garnet, pyroxene, epidote and amphibole, whereas sulfides mainly contain chalcopyrite, galena, sphalerite, pyrite and pyrrhotite. Electron microprobe analyses indicate that the garnet is compositionally predominated by andradite molecules （And= 59.00%-97.70%） and grossular molecules （Gro= 1.92 %- 40. 42%）, therefore belonging to the andradite-grossular series; pyroxene is predominated by diopside molecules （Di=45% -91%） and hedenbergite molecules （Hd= 8%-53%）, therefore manifesting as diopside and minor hedenbergite; amphibole belongs to the tremolite-actinolite series, although its composition varies greatly. Mineral assemblages and chemical compositions suggest that the skarn in the Weixi block is typical of calcic skarn. Moreover, the chemical components of garnet with zoning vary in a regular way that Al2 O3 contents increase and then decrease while FeOTdecreases and then increases. The process shows metasomatism occurred along with change of pH in the ore-forming fluid continuously from weak acidic-alkaline to neutral condition and ultimately to weak acidic-alkaline conditio

关 键 词：钙矽卡岩 电子探针 维宝矿床 新疆 祁漫塔格 

分 类 号：P618.4[天文地球—矿床学]