投稿时间：2014-07-02
修订日期：2014-10-23
网络发布日期：2014-12-30
中文摘要:曹四夭钼矿床位于内蒙古兴和县,是近年来在华北克拉通北缘发现的一个超大型斑岩钼矿床。矿体主要赋存于中生代花岗斑岩与中太古界集宁群变质岩接触带靠近变质岩一侧,成矿与晚侏罗世正长花岗斑岩密切相关。该矿床的成矿过程可以划分为3个阶段:石英-辉钼矿阶段、石英-辉钼矿-黄铁矿阶段、石英-方解石-黄铁矿阶段。流体包裹体研究表明,曹四夭钼矿床主要发育富液包裹体(WL型)、富气包裹体(WG型)、H2O-CO2包裹体(C型)和含子矿物包裹体(S型)。正长花岗斑岩的石英斑晶内发育WL型、WG型、C型和S型包裹体,其均一温度介于385~550℃,w(NaCleq)介于8.0%~65.0%,属H2O-NaCl-CO2-CH4体系;石英-辉钼矿阶段的石英内亦发育WL型、WG型、C型和S型包裹体,其均一温度介于243~401℃,w(NaCleq)介于6.0%~40.7%,属H2O-NaCl-CO2±CH4体系;石英-辉钼矿-黄铁矿阶段的石英内主要发育WL型和S型包裹体,亦有少量WG型和C型包裹体,其均一温度介于208~336℃,w(NaCleq)介于1.2%~34.1%,属H2O-NaCl±CO2体系;石英-方解石-黄铁矿阶段的石英内仅发育WL型包裹体,其均一温度为124~196℃,w(NaCleq)介于3.9%~13.2%,属H2O-NaCl体系。曹四夭钼矿床石英-辉钼矿阶段和石英-辉钼矿-黄铁矿阶段成矿热液的δ18O水值介于4.1‰~7.5‰,δDV-SMOW值为-96.0‰~-76.9‰;石英-方解石-黄铁矿阶段成矿热液的δ18O水值介于-2.9‰~-0.5‰,δDV-SMOW值介于-112.2‰~-77.7‰。表明钼成矿阶段的流体主要来自岩浆水,而石英-方解石-黄铁矿阶段有明显的大气降水注入。石英-辉钼矿阶段和石英-辉钼矿-黄铁矿阶段的流体均为不混溶流体,流体的多次沸腾和氧逸度的降低是矿质沉淀的2种主要机制。
Abstract:The Caosiyao deposit in Xinghe County of Inner Mongolia is a newly discovered superlarge porphyry Mo deposit in the central segment of the northern margin of the North China Craton. The orebodies of the deposit dominantly occur in metamorphic rocks of the Jining Group, close to the contact zone between the Mesozoic granite porphyry and the Jining Group; the deposit is genetically closely related to the late Jurassic syenogranite porphyry in the ore district. The ore-forming process in the deposit can be divided into three stages: quartz-molybdenite stage, quartz-molybdenite-pyrite stage, and quartz-calcite-pyrite stage. Four types of fluid inclusions were recognized in quartz phenocrysts and various quartz veins. Fluid inclusions include liquid-rich (WL type), gas-rich (WG type), H2O-CO2 (C type) and daughter mineral-bearing (S type) inclusions. The fluid inclusions in quartz phenocrysts of the syenogranite porphyry are composed of WL-, WG-, C- and S-types; their homogenization temperatures and w(NaCleq) vary from 385℃ to >550℃ and 8.0% to 65.0%, respectively; the fluid at this stage generally belongs to the H2O-NaCl-CO2-CH4 system. The fluid inclusions in quartz of the quartz-molybdenite stage also consist of WL-, WG-, C- and S-types; their homogenization temperatures and w(NaCleq) vary from 243℃ to 401℃ and 6.0% to 40.7%, respectively; the fluid of this stage generally belongs to the H2O-NaCl-CO2±CH4 system. The fluid inclusions in quartz of the quartz-molybdenite-pyrite stage are mainly of WL- and S-types, with a small amount of WG- and C- types; their homogenization temperatures and w(NaCleq) vary from 208℃ to 336℃ and 1.2 % to 34.1%, respectively; the fluid of this stage generally belongs to the H2O-NaCl±CO2 system. The fluid inclusions in quartz of the quartz-calcite-pyrite stage only comprise WL type with homogenization temperatures and w(NaCleq) of 124℃ to 196℃ and 3.9% to 13.2%, respectively; the fluid of this stage generally belongs to the H2O-NaCl system. The δ18OH2O and δDV-SMOW values of ore-forming hydrothermal fluids of the quartz-molybdenite and quartz-molybdenite-pyrite stages are 4.1‰~7.5‰ and -96.0‰~-76.9‰, respectively; whereas the corresponding values of the quartz-calcite-pyrite stage are -2.9‰~-0.5‰ and -112.2‰~-77.7‰, respectively. The H-O isotope analytical results indicate that the ore-forming fluids of the quartz-molybdenite and quartz-molybdenite-pyrite stages were primarily magmatic and those of the quartz-calcite-pyrite stage were mixed fluids of magmatic water and meteoric water. Fluids of the quartz-molybdenite and quartz-molybdenite-pyrite stages are both immiscible fluids, and the multiepisode fluid boiling and oxygen fugacity decreasing constituted two dominant mechanisms for mineral deposition.
keywords:geochemistry fluid inclusion hydrogen-oxygen isotope porphyry Mo deposit Caosiyao Inner Mongolia the northern margin of the North China Craton
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中图分类号：P618.65
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基金项目:本文得到内蒙古自治区地质勘查基金项目(编号:201203YS01)和国家自然科学基金项目(编号:41172081)的资助
引用文本：
王国瑞,武广,吴昊,刘军,李香资,许立权,张彤,权知心.2014.内蒙古兴和县曹四夭超大型斑岩钼矿床流体包裹体和氢-氧同位素研究[J].矿床地质,33(6):1213~1232WANG GuoRui,WU Guang,WU Hao,LIU Jun,LI XiangZi,XU LiQuan,ZHANG Tong,QUAN ZhiXin.2014.Fluid inclusion and hydrogen-oxygen isotope study of Caosiyao superlarge porphyry molybdenum deposit in Xinghe County, central Inner Mongolia[J].Mineral Deposits33(6):1213~1232
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