藏南扎西康锑铅锌银矿床矿物学特征及成因意义

发布时间：2018-08-14 11:12

【摘要】：扎西康矿床位于北喜马拉雅金锑成矿带,关于其成矿环境及演化特征尚缺乏系统的研究。而铅锌矿床中通过典型矿物的矿物学特征的研究对于指示成矿环境和成矿过程具有重要的指示意义。本文在系统划分扎西康矿床成矿期次(两期六阶段)的基础上,并分别按照硫化物、硫盐矿物、含银矿物等类别对扎西康矿床开展了矿物学研究。扎西康矿床闪锌矿存在三个世代,第一世代闪锌矿主要呈他形粒状产于细纹层状锰铁碳酸盐;第二世代闪锌矿主要呈他形粒状产于团块状,球状,环状构造矿石;第三世代闪锌矿主要呈角砾状产于石英脉中。扎西康矿床闪锌矿形成早期富Fe、Mn,贫Zn;晚期贫Fe、Mn,富Zn。硫锑铅矿主要以针状集合体被闪锌矿包裹,或呈他形粒状大量充填在石英晶隙中,或呈他形被黄铜矿,锰铁碳酸盐等包裹,还有部分以自形针状生长在矿物表面;脆硫锑铅矿呈微细他形粒状充填在石英晶隙中,共生矿物是石英、毒砂和黄铁矿;车轮矿主要呈微细他形粒状分布在方铅矿中或在方铅矿周边形成环边,共生矿物是方铅矿、银黝铜矿和黄铜矿;银黝铜矿主要呈微细他形粒状分布,共生矿物是方铅矿、车轮矿、硫锑铅矿。S同位素地质温度计显示扎西康第二、三成矿阶段温度分别是242℃~325℃、317℃。闪锌矿的FeS分子百分含量与硫逸度的关系,硫盐矿物组合与温度和S逸度的关系显示,扎西康一至五成矿阶段的硫逸度分别为-13.9~-13.2、-14.5~-13.6、-13.3~-9.8、-14.6~-15.6、-16.9~-14.9。表明扎西康矿床成矿早期硫逸度较低,外部流体混合使第三成矿阶段硫逸度突然升高并随着成矿进行逐渐降低。锰铁碳酸盐中Mn/Fe比值为1.55~0.87,显示第一成矿期成矿流体处于强还原环境,并且富含CO2。扎西康矿床第一成矿期成矿流体随着温度下降Zn~(2+)、Pb~(2+)大量晶出成矿。第二成矿期成矿流体温度升高,二世代闪锌矿和方铅矿发生活化、再交代作用。成矿流体混合外部流体使硫逸度上升,大量闪锌矿和富Ag方铅矿晶出。进入第四成矿阶段Pb~(2+)、Sb~(2+)、Ag+、Fe~(2+)、、Zn~(2+)、Cu~(2+)等形成独立银矿物。随着Ag~+、Zn~(2+)完全消耗,Pb~(2+)和Sb~(2+)主要形成以Pb-Sb硫盐为主的矿物,Fe~(2+)主要形成黄铁矿和毒砂,随着Fe~(2+)、Pb~(2+)消耗完全,成矿流体中Sb~(2+)以辉锑矿的形式沉淀,成矿物质消耗完毕,最后以石英±方解石的形式结束矿化活动。
[Abstract]:The Zaxikang deposit is located in the gold and antimony metallogenic belt of the northern Himalayas. There is no systematic study on its metallogenic environment and evolution characteristics. The study of mineralogical characteristics of typical minerals in lead-zinc deposits is of great significance in indicating the metallogenic environment and metallogenic process. On the basis of systematically dividing the metallogenic stages (two phases and six stages) of the Zaxikang deposit, the mineralogical study of the Zaxikang deposit has been carried out according to the types of sulfides, sulphide minerals and silver-bearing minerals. There are three generations of sphalerite in Zaxikang deposit, the first generation of sphalerite mainly occurs in fine lamellar ferromanganese carbonate, the second generation of sphalerite is mainly allograined, spherical and annular structural ore. The third generation sphalerite mainly occurs in quartz vein in the form of breccia. The sphalerite of Zaxikang deposit was rich in Fe ~ (2 +) and Zn in the early stage, and was rich in Fe ~ (2 +) and Zn ~ (2 +) in the late period. Sb-S is mainly encapsulated by sphalerite as acicular aggregates, or filled in quartz intercalations in the form of heteromorphic granulites, or wrapped in chalcopyrite, ferromanganese carbonate, etc., and some of them grow on the surface of minerals in the form of self-shaped needles. The brittle antimony lead ores are filled in quartz crystal interstices in the form of microfine antimony grains, and the symbiotic minerals are quartz, arsenopyrite and pyrite, while the wheel ores are mainly distributed in the galena or form ring edges around the galena, and the symbiotic minerals are galena. Silver tetrahedrite and chalcopyrite, silver tetrahedrite are mainly distributed in the form of microalloid granulites, and the symbiotic minerals are galena, wheel ore, sulphoantimonite. S isotopic geothermometer shows that the temperature of the second and third metallogenic stages of Zaxikang is 242 鈩，

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