投稿时间：2011-09-07
修订日期：2011-12-01
中文摘要:秋树湾铜钼矿是东秦岭钼矿带上典型的受斑岩体控制的矽卡岩-斑岩角砾岩筒复合型矿床,矿体赋存于成矿母岩花岗岩及矽卡岩和角砾岩筒中。根据矿物共生组合、矿石组构、围岩蚀变及脉体的穿插关系,可划分为早(Ⅰ)、中(Ⅱ)、晚(Ⅲ)3个矿化期,再将Ⅰ期细分为干矽卡岩-钾长石化-石英阶段(Ⅰ1)、爆破角砾岩阶段(Ⅰ2)、湿矽卡岩阶段(Ⅰ3)、磁铁矿阶段(Ⅰ4);Ⅱ期分为斑岩型铜(钼)矿阶段(Ⅱb)和石英硫化物阶段(Ⅱs);Ⅲ期为方解石、重晶石、石英阶段(Ⅲ)。流体包裹体可划分为S型含子矿物多相包裹体、L型纯液相包裹体、C型含CO2三相包裹体、W型气液两相包裹体、G型纯气相包裹体5种类型。按时间先后顺序,成矿流体的温度、盐度、氧化还原环境具有规律性的演化特征。均一温度范围: Ⅰ期为222~406℃,Ⅱ期为152~315℃,Ⅲ期为119~189℃;盐度w(NaCleq): Ⅰ期介于4.2%~36.5%,Ⅱ期为3.3%~34.8%,Ⅲ期为4.2%~11.9%。激光拉曼光谱及群体包裹体成分分析结果表明,第Ⅰ期流体以H2O、CO2、CH4、H2S为主,表现为还原环境;第Ⅱ期流体以H2O、CO2、N2、O2、SO42-、Cl-、F-为主,为氧化环境,暗示流体源于岩浆。流体包裹体岩相学及包裹体测温表明,流体由早期的高温、高盐度、含CO2的H2O-NaCl-CO2体系的岩浆流体在成矿Ⅰ期发生沸腾作用和相分离,伴随着流体沸腾、CO2逸失、温度下降、大气水的加入、盐度下降等过程,导致大量金属硫化物沉淀。在成矿Ⅱ、Ⅲ期成矿体系趋于开放,流体存在大气降水混入,逐渐演化为晚期的低盐度、中低温度、贫CO2的流体体系。H、O、S同位素结果表明有地幔流体参与成矿作用。
Abstract:The Qiushuwan copper-molybdenum deposit in the East Qinling molybdenum belt is atypical skarn-porphyry breccia pipe controlled by the porphyry. Ore bodies occur in the biotite granite porphyry, skarn and breccia pipes. According to mineral paragenesis, ore fabrics, wall-rock alteration and intersecting relationship of the veins, the formation of the ore deposit can be divided into three periods, i.e., high-temperature alteration-skarn period (Ⅰ), sulfide precipitation period (Ⅱ) and low-temperature mineral-free period (Ⅲ), composed of six ore-forming stages: dry skarn-K-feldspar-quartz stage (Ⅰ1), explosion breccia stage (Ⅰ2), wet skarn stage (Ⅰ3), magnetite stage (Ⅰ4), porphyry copper (molybdenum) ore stage (Ⅱb) and quartz sulfide mineralization (Ⅱs), and calcite, barite, quartz stage (Ⅲ). Mineral-forming fluids in quartz, garnet and calcite can be divided into five types, i.e., S-type multi-phase inclusions containing daughter minerals, L-type pure liquid inclusions, C-type three-phase CO2-bearing inclusions, W-type gas-liquid two-phase inclusions, and G type pure gas inclusions. Ore-forming fluid temperature, salinity and redox environment are characterized by regular evolution: homogenization temperature values of Ⅰ period, Ⅱ period and Ⅲ period are 222~406℃, 152~315℃, and 119~189℃ respectively, whereas salinities w(NaCleq) of Ⅰ period, Ⅱ period and Ⅲ period are 4.2%~36.5%, 3.3%~34.8% and 4.2%~11.9%, respectively; Raman spectroscopy and analysis of group inclusions show that the fluid compositions are mainly H2O,CO2, CH4, H2S in Ⅰ period, implying a reduction environment, H2O, CO2, N2, O2, SO42-, Cl-, F- in Ⅱ period, suggesting an oxidation environment and the derivation of fluid from the magma. Inclusions petrography and thermometry shows that the fluid was originally high temperature, high salinity, CO2-bearing H2O-NaCl-CO2 system magmatic fluid, and experienced boiling and phase separation in Ⅰ period, accompanied by fluid boiling, CO2 escaping, temperature drop, addition of atmospheric water, and decrease of salinity, which led to the precipitation of large quantities of metal sulfides. In Ⅱ and Ⅲ period, the ore-forming system tended to become open, and meteoric water infiltrated into the fluid, leading to the evolution into the late low-salinity, low temperature, poor CO2 fluid system. H, O, S isotopes show that mantle materials participated in the ore-forming process.
文章编号：
中图分类号：P611.1;P597.2
文献标志码：
基金项目:本文得到科技部国家"十一五"科技支撑计划(2006BA01B07)、湖南省创新基金(CX2010B104)和中南大学优秀博士生基金(2010ybfz050)联合资助
引用文本：
秦臻,戴雪灵,邓湘伟.2012.东秦岭秋树湾铜钼矿流体包裹体和稳定同位素特征及其地质意义[J].矿床地质,31(2):323~336QIN Zhen,DAI XueLing,DENG XiangWei.2012.Fluid inclusions and stable isotopes of Qiushuwan copper-molybdenum deposit in East Qinling orogenic belt and their geological implications[J].Mineral Deposits31(2):323~336
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