Fluid inclusion study of the Bainaimiao Cu-Au deposit in Inner Mongolia, China

内蒙古白乃庙铜金矿床位于华北板块北缘增生型造山带,石英脉型和蚀变岩型矿体受 EW 向韧-脆性剪切带控制。成矿过程分为三个阶段:早阶段石英-黄铁矿,乳白色石英和粗粒黄铁矿变形、破碎;中阶段多金属硫化物充填胶结早阶段变形、破碎的石英角砾和黄铁矿裂隙;晚阶段为石英-碳酸盐细脉,穿切早中阶段脉体和矿物组合。冷热台显微测温结果显示,早阶段石英中原生流体包裹体的均一温度为248℃～380℃,盐度为4.34%～6.59%,次生包裹体均一温度为180℃～260℃,盐度为3.23%～4.18%NaCl eqv;中阶段石英中原生包裹体的均一温度变化范围为215℃～241℃,盐度为2.90%～4.18%NaCl e...The Bainaimiao Cu-Au deposit is located at the north margin of the north China craton. Cu-bearing lodes and altered ores are controlled by EW-trending faults. The hydrothermal ore-forming process can be divided into early, middle and late stages, characterized by quartz-pyrite, polymetallic sulfides and carbonate-quartz, respectively. The early stage veins and minerals are structurally deformed and broken, suggesting that they had formed in a compressional or transcompressional setting. The middle stage polymetallic sulfides are intruded into the early stage veins and cracks, and show no deformation, which suggests they formed in a tensional shear setting and had not undergone compression. The late stage quartz-carbonate veinlets cut the early and middle stage veins and minerals. The homogenization temperatures of the primary H2O-rich fluid inclusions in the early stage quartz range from 24890 to 380 degrees C and their salinities range from 4. 34% to 6. 59% NaCl equivalent. The homogenization temperatures of the secondary H2O-rich fluid inclusions in the early stage quartz range from 18090 to 260 degrees C and their salinities range from 3. 23% to 4. 18% NaCl equivalent. The homogenization temperatures of the primary H2O-rich fluid inclusions in the middle stage quartz range from 215 0 to 24190 and their salinities range from 2. 90% to 4. 18% NaCl equivalent, which are similar to those of the secondary H2O-rich fluid inclusions in the early stage quartz. The homogenization temperature of H20-rich fluid inclusions in late stage quartz and calcite range from 13790 to 180 degrees C with salinities of 0. 50 to 2. 00% NaCl equivalent. Gases in fluid inclusions are CO2, CH4, and N-2. The ore fluid of the Bainaimiao Cu-Au deposit is characterized by low salinity, low density and enrichment in CO2. When this kind of fluid reached shear zones, the pressure of the ore fluid became much lower immediately and the fluid boiled and CO2 separated. The ore fluid became oversaturation and precipitated sulfide ores. Therefore, the Bainaimiao Cu-Au deposit could be taken as an example of orogenic-type Cu-Au deposits due to its similarities in ore geology and ore fluids compared with the orogenic deposits in the world.SCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)中国科学引文数据库(CSCD)0092165-21762