内蒙古拜仁达坝银铅锌多金属矿床成矿流体特征及其演化  

Characteristics and evolution of ore-forming fluids in Bairendaba Ag-Pb-Zn polymetallic deposit, Inner Mongolia

作　　者：王祥东[1] 吕新彪[1,2] 梅微[1] 唐然坤[1] 李春诚[1] 

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《矿床地质》2014年第2期406-418,共13页Mineral Deposits

基　　金：国家科技支撑计划重点项目(NO.2007BA25B04;2011BAB06B04-05);内蒙古矿调项目(NO.NMKD2010-3)联合资助

摘　　要：拜仁达坝银铅锌多金属矿床位于内蒙古大兴安岭西坡南缘成矿带，矿体主要赋存于海西期石英闪长岩中，受断裂控制明显。通过系统的矿相学、流体包裹体、激光拉曼光谱和氢、氧同位素研究，表明拜仁达坝银铅锌多金属矿床属于中温岩浆热液脉状矿床，热液成矿期可以分为4个阶段，前3个成矿阶段温度区间分别为238～397℃、164--328℃、150--266℃。锌矿化主要集中在Ⅱ阶段，银、铅矿化主要集中在第Ⅲ阶段。初始的成矿流体为含CH4和（弛的盐水体系，随着温压的逐渐降低，导致CO2、CH4开始逃逸，而演化成盐水体系。各阶段成矿流体的温度和盐度彼此重叠，体现出很好的继承性和连续演化的特征。笔者认为流体中CH4、CO2逃逸和大气降水混入导致Ag、Pb、Zn矿化，燕山期岩浆活动导致成矿流体聚集，而二叠系为成矿提供了有机物和金属元素，裂隙发育的石英闪长岩则提供了容矿空间。The Bairendaba Ag-polymetallic deposit is located in the south metallogenic belt on the western slope of the Da Hinggan Mountains within Inner Mongolia, and orebodies are mainly hosted in the Hercynian quartz-diorite controlled obviously by the fracture. A study of ore petrography and fluid inclusions and DXR laser Raman analysis as well as hydrogen oxygen isotope geochemistry show that the Bairendaba Ag-polymetallic deposit belongs to a mesothermal magmatic hydrothermal vein deposit, and the hydrothermal mineralization can be divided into 4 stages, with the homogenization temperatures of the first three metallogenic stages being 238- 397℃, 164-328℃ and 150--266℃ respectively. Zn mineralization occurred at the second stage, whereas Ag and Pb mineralization occurred at the third stage. The ore-forming fluid was originally a CH4 and CO2-bearing brine sys- tem, and then evolved into a brine system through the release of CO2 and CH4 along with decreasing temperature and pressure. The temperature and salinity of ore-forming fluid were superimposed upon each other from early to late, suggesting the characteristics of succession and continuous evolution. Studies show that the escape of CO2 and CH4 and the input and mixing of meteoric water caused Ag, Pb, Zn deposition. The magrnatic activity of Yanshanian period resulted in the concentration of the ore-forming fluids, the Permian strata provided organic matter and metal elements, and the fissures of quartz-diorite supplied the ore-forming space.

关 键 词：地球化学 流体包裹体 成矿流体 氢氧同位素 拜仁达坝 

分 类 号：P618.52[天文地球—矿床学]