内蒙古维拉斯托Zn-Cu-Ag矿床硫同位素及成矿物理化学条件研究  

Research on sulfur isotopes and metallogenic physicochemical conditions of Weilasituo Zn-Cu-Ag deposit,Inner Mongolia

作　　者：董锡泽 杨贺 樊金虎[2] 孙立秋[2] 王可勇[1] 马万里 DONG Xi-ze;YANG He;FAN Jin-hu;SUN Li-qiu;WANG Ke-yong;MA Wan-li(College of Earth Sciences,Jilin University,Changchun 130061,China;The Fifth Geological Group Limited Liability Company of Liaoning Province,Yingkou 115100,Liaoning,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]辽宁省第五地质大队有限责任公司,辽宁营口115100

出　　处：《世界地质》2019年第4期953-961,共9页World Geology

基　　金：内蒙古山金地质矿产勘查有限公司科研项目(SJDK-KY2017-5);中国地质调查局中国科学技术部项目(2017YFC0601304)联合资助

摘　　要：维拉斯托Zn-Cu-Ag矿床是大兴安岭南段典型的热液脉型矿床,赋存在海西期的石英闪长岩和古元古代片麻岩中,矿区东部主要发育的Zn-Cu-Ag矿化,多赋存于近EW向的压扭性断裂构造带中;矿区西部多发育Sn矿化,主要赋存于石英斑岩体顶部及其上部的石英脉中。维拉斯托矿床存在4个成矿阶段:Ⅰ阶段:黄铁矿-毒砂-石英阶段;Ⅱ阶段:黄铁矿-磁黄铁矿-黄铜矿-闪锌矿-石英阶段;Ⅲ阶段:黄铁矿-黄铜矿-方铅矿-石英-方解石阶段;Ⅳ阶段:贫硫化物-方解石阶段。其中Ⅱ、Ⅲ阶段为主成矿阶段。在本次工作中,根据主成矿阶段的矿物硫同位素组成及成矿温度,利用公式δ^34S(i)-δ^34S(H2S)=A*10^6/T^2+B*10^3/T+C,计算了主成矿阶段成矿热液的δ^34S(H2S)值。Ⅱ阶段δ^34S(H2S)为1.7×10^-3^-1.9×10^-3,Ⅲ阶段δ34S(H2S)为1.4×10^-3^-4.7×10^-3。此外,根据硫同位素非质量分馏和矿物平衡关系热力学原理,构建300℃,500 bars下,硫同位素及矿物平衡关系的热力学模型,估算了主成矿阶段的物理化学条件。维拉斯托矿床Ⅱ阶段的成矿物理化学条件约为-35.8<log fO2<-40.8、5.2<pH<7.7、log fS2≈-12,Ⅲ阶段的成矿物理化学条件约为-34.8<log fO2<-37.5、5.8<pH<7.7、log fS2≈-10,维拉斯托矿床在主成矿阶段表现出向高氧逸度和高硫逸度转变的趋势,同时,δ^34S(ΣS)被估算为-2×10^-3,验证了维拉斯托矿床硫来源为岩浆。The Weilasituo Zn-Cu-Ag deposit is a typical hydrothermal vein deposit in the south of Great Xing’an Range,which is hosted in Hercynian quartz diorite and Paleoproterozoic gneiss.The Zn-Cu-Ag mineralization is mainly developed in the eastern part of the mining area,which is mostly occurred in the EW-trending compress-transitional fault belt;and the Sn mineralization is mainly developed in the western part,which is mostly occursed in the top and upper quartz veins of quartz porphyry.There are four metallogenic stages in the Weilasituo deposit:stageⅠ:pyrite-arsenopyrite-quartz stage;stageⅡ:pyrite-pyrrhotite-chalcopyrite-sphalerite-quartz stage;stageⅢ:pyrite-chalcopyrite-galena-quartz-calcite stage;stageⅣ:deficient sulfide-calcite stage.The stagesⅡandⅢare main metallogenic stages.In this work,theδ^34S(H2S)value of ore-forming hydrothermal solution in the main ore-forming stage is calculated by formulaδ^34S(i)-δ^34S(H2S)=A*10^6/T^2+B*10^3/T+C according to the sulfur isotopic composition and ore-forming temperature of minerals in the main ore-forming stage.Theδ^34S(H2S)of stageⅡis 1.7×10^-3^-1.9×10^-3,while theδ34S(H2S)of stageⅢis 1.4×10^-3^-4.7×10^-3.In addition,according to the thermodynamic principle of the relationship between non mass fractionation of sulfur isotopes and mineral equilibrium,a thermodynamic model of sulfur isotope and mineral equilibrium relationship at 300℃ and 500 bars is established to estimate the physical and chemical conditions of the main mineralization stages.The ore-forming physicochemical conditions of stageⅡin the Weilasituo deposit are about 35.8<log fO2<-40.8,5.2<pH<7.7,log fS2≈-12,and the ore-forming physicochemical conditions of stageⅢare-34.8<log fO2<-37.5,5.8<pH<7.7 and log fS2≈-10.The Weilasituo deposit shows a trend of transition to high oxygen fugacity and high sulfur fugacity during the main mineralization stages.Meanwhile,δ^34S(ΣS)is estimated to be-2×10^-3,which verifies that the sulfur of the Weilasituo deposit is from magma.

关 键 词：内蒙古 维拉斯托矿床 热力学模型 

分 类 号：P618.4[天文地球—矿床学] P611.5[天文地球—地质学]