投稿时间：2014-07-27
修订日期：2014-10-20
网络发布日期：2014-12-30
中文摘要:内蒙古卓资县大苏计钼矿床位于华北克拉通北缘中段的凉城断隆内,是近年来在华北克拉通北缘发现的一个大型斑岩钼矿床,矿体主要产于印支期石英斑岩和正长花岗斑岩中。成矿过程可以划分为石英-钾长石-黄铁矿±辉钼矿±磁铁矿阶段(早阶段)、石英-绢云母-辉钼矿-黄铁矿阶段(中阶段)和石英-方解石-黄铁矿±闪锌矿±方铅矿阶段(晚阶段)。矿石中5件辉钼矿的Re-Os同位素模式年龄介于(223.6±3.1) Ma~(224.2±3.4)Ma之间,其加权平均值为(223.9±1.4)Ma(MSWD=0.017),等时线年龄为(223.5±5.5)Ma(MSWD=0.026),表明大苏计钼矿床形成于印支期。大苏计钼矿床发育富液型、富气型、H2O-CO2型、含子矿物型和纯气相包裹体。成矿早阶段主要发育富液型、富气型包裹体,另有少量H2O-CO2型包裹体,其均一温度介于342~430℃之间,盐度w(NaCleq)介于3.4%~11.0%之间;中阶段主要发育富液型、富气型、H2O-CO2型和含子矿物型包裹体,另有少量纯气相包裹体,其均一温度为234~380℃之间,盐度w(NaCleq)介于6.2%~34.9 %之间;晚阶段仅发育富液型包裹体,其均一温度介于202~280℃之间,盐度w(NaCleq)介于1.2%~11.7%之间,指示该阶段有大气降水的加入。成矿流体从早、中阶段的H2O-NaCl-CO2体系演化为晚阶段的H2O-NaCl体系。早、中阶段流体均为不混溶流体,流体沸腾是成矿物质沉淀的主要机制。集宁地区钼矿床主要为斑岩型,至少存在晚三叠世和晚侏罗世2期钼成矿事件。
Abstract:The Dasuji deposit of Inner Mongolia, located in the Liangcheng uplift, is a newly discovered large porphyry Mo deposit in the central segment of the northern margin of the North China Craton. The orebodies of the deposit dominantly occur within the Indosinian quartz porphyry and syenogranite porphyry. The ore-forming process in the deposit can be divided into three stages: the early quartz-potassium feldspar-pyrite±molybdenite±magnetite stage, the middle quartz-sericite-molybdenite-pyrite stage, and the late quartz-carbonate-pyrite±sphalerite±galena stage. Re-Os dating of five molybdenite samples yielded model ages of (223.6±3.1) Ma~(224.2±3.4) Ma, with a weighted mean age of (223.9±1.4) Ma (MSWD=0.017) and an isochron age of (223.5±5.5) Ma (MSWD=0.026), indicating that the Dasuji deposit formed in Indosinian period. Five types of fluid inclusions in quartz veins were recognized, i.e., liquid-rich, gas-rich, H2O-CO2, daughter mineral-bearing, and pure gas inclusions. The fluid inclusions of the early stage are mainly liquid-rich and gas-rich types, with a small amount of H2O-CO2 type; their homogenization temperatures and salinities vary from 342 ℃ to 430 ℃ and from 3.4% to 11.0%, respectively. The inclusions of the middle stage are mainly liquid-rich, gas-rich, H2O-CO2, and daughter minerals-bearing types, with a small amount of pure gas type; these types have homo- genization temperatures and salinities of 234~380 ℃ and 6.2%~34.9%, respectively. The late stage only comprises liquid-rich inclusions with homogenization temperatures and salinities of 202~280 ℃ and 1.2%~11.7%, respectively, indicating that ore-forming fluid of this stage is significantly mixed with meteoric water. The ore-forming fluids evolved from an H2O-NaCl-CO2 system of the early and middle stages to an H2O-NaCl system of the late stage. Both early- and middle-stage fluids are immiscible fluid, and the multi-episode fluid boiling seem to have been the dominant mechanism for mineral deposition. Porphyry Mo deposit is the most important Mo deposit type, and there are at least two periods of porphyry Mo mineralization in the Jining area: late Triassic and late Jurassic.
keywords:geochemistry molybdenite Re-Os dating fluid inclusion porphyry Mo deposit Dasuji 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：
吴昊,武广,陶宏,王国瑞,李铁刚,陈军其,杨宁宁.2014.内蒙古卓资县大苏计斑岩型钼矿床辉钼矿Re-Os同位素年龄及流体包裹体研究[J].矿床地质,33(6):1251~1267WU Hao,WU Guang,TAO Hong,WANG GuoRui,LI TieGang,CHEN JunQi,YANG NingNing.2014.Molybdenite Re-Os dating and fluid inclusion study of Dasuji porphyry molybdenum deposit in Zhuozi County, central Inner Mongolia[J].Mineral Deposits33(6):1251~1267
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