青海省都兰县果洛龙洼金矿成矿流体

Ore-Forming Fluid of the Guoluolongwa Gold Deposit in Dulan County,Qinghai Province

果洛龙洼金矿是青海东昆仑地区最典型、最具规模的金矿床之一。在前人资料基础上,将果洛龙洼金矿热液成矿期划分为4个成矿阶段:贫矿化石英阶段、石英-多金属硫化物阶段(主要成矿阶段)、石英-贫硫化物阶段(次要成矿阶段)和石英-碳酸盐阶段。随后对主要和次要成矿阶段石英脉开展流体包裹体显微测温和H-O同位素研究。结果表明:原生流体包裹体主要包括气液两相、富CO2三相、纯CO2两相共3类;成矿流体总体以CO2-NaCl-H2O体系为主,均一温度为130.0～357.3℃,盐度(w(NaCl))为1.83%～20.11%。石英-多金属硫化物阶段石英δ18 OV-SMOW值为14.8‰～17.2‰,据此计算流体的δ18 OH2O值为5.5‰～8.5‰,流体的δDV-SMOW值为-61‰～-96‰;而石英-贫硫化物阶段石英δ18 OV-SMOW值为15.7‰～16.9‰,据此计算流体的δ18 OH2O值为4.1‰～5.3‰,流体的δDV-SMOW值为-84‰～-101‰。由此认为:主要成矿阶段成矿流体可能为高温低盐度富CO2变质热液和低温中高盐度岩浆热液两个端元组成的混合流体;次要成矿阶段成矿流体主要为混合后更均匀的中低温中低盐度热液,但后期明显有大气降水混入。总之,成矿流体的来源、性质及其演化等方面的研究结果进一步证明果洛龙洼金矿为造山型金矿。

The Guoluolongwa gold deposit is one of the most typical and largest gold deposits in Eastern Kunlun belt, Qinghai Province. Combining predecessors ~ researches, authors divide the hydrothermal mineralization in Guoluolongwa deposit into four stages, i.e. sulfide-barren and quartz, quartz and polymetallic sulfide （major metallogenic stage）, quatz-barren and sulfide （minor metallogenic stage）, as well as quartz and carbonate ones. Then we carried microthermometric and H - O isotopic analysis for quartz veins formed in the major and minor mineralization stages. The results indicate that types of primary fluid inclusion include two-phase aqueous, three-phase CO2-bearing and two-phase CO2 fluid inclusion. The ore-forming fluid is the CO2 - NaC1 - H20 hydrothermal system, with the homogenization temperature from130.0 ℃ to 357.3 ℃ and salinity from 1.83% to 20. llwt^NaC1. The quartz mineral formed in the quartz-polymetallic sulfide stage has the 8TM OV--SMOW value from 14. 8N0 to 17.2%0 and values from 5.5%0 to 8.5%0. The 6Dv SMOW value in fluid inclusions within the quartz mineral varies from --61%0 to --96O/oo0. The quartz formed in the quartz barren sulfide stage has c^lS（）v svow value from 15. 7%0 to 16. 9%0, calculated values from 4. 1%0 to 5. 3%0, #Dv SMOW values from --84%~ to --101%0. According to the data in this paper, we thought that the major ore forming fluid derived from mixed fluids of high-temperature, low-salinity, COe rich metamorphic water with low temperature, intermediate-high-salinity magmatic water; and the minor ore-forming fluid was changed into more homogeneous intermediate-low-temperature and intermediate-low-salinity fluid, with apparent mixing of the meteoric water in the late stage. In a word, it can be concluded further that the Guoluolongwa gold deposit belongs to the orogenic gold deposit due to the origin, characters and evolutions of ore-forming fluids.