Abstract:

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-NaCl-H₂O hydrothermal system, with the homogenization temperature from130.0 ℃ to 357.3 ℃ and salinity from 1.83% to 20.11wt%NaCl. The quartz mineral formed in the quartz-polymetallic sulfide stage has the δ¹⁸O_V-SMOW value from 14.8‰ to 17.2‰ and   values from 5.5‰ to 8.5‰. The δD_V-SMOW value in fluid inclusions within the quartz mineral  varies from -61‰ to -96‰. The quartz formed in the quartzbarren sulfide stage  has δ¹⁸O_V-SMOW value from 15.7‰ to 16.9‰, calculated   values from 4.1‰ to 5.3‰, δD_V-SMOW values from -84‰ to -101‰. According to the data in this paper, we thought that the major ore-forming fluid derived from mixed fluids of high-temperature, low-salinity, CO₂-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.

Key words: Guoluolongwa gold deposit, microthermometry of fluid inclusions, H-O isotopes, orogenic gold deposit