关键词: 流体包裹体, 成矿流体来源, 矿床成因, 金牙卡林型金矿床, 滇黔桂“金三角”

Abstract: Jinya gold deposit is one of the typical Carlin-type gold deposits in the “Golden Triangle” area of Yunnan, Guizhou and Guangxi provinces. The ore bodies are obviously controlled by fault structures and are mainly layered, pod-shaped, and lenticular in argillaceous siltstone and silty mudstone of the Middle Triassic Baifeng Formation. In order to explore the metallogenic fluid properties and mineralization mechanism, the petrographic study, micro temperature measurement and Laser Raman spectroscopy analysis on the fluid inclusions in the study area were carried out. The metallogenic hydrothermal process of this deposit can be divided into three metallogenic stages: Quartz-pyrite stage (Ⅰ), pyrite-arsenopyrite stage (Ⅱ) and quartz-carbonate stage (Ⅲ), and stage Ⅱ is the main metallogenic stage. The petrographic study of fluid inclusions shows that the fluid inclusions in the metallogenic period are mainly two-phase vapor inclusions, and the liquid phase is mainly water; The gas composition is mainly CO2, N2, SO2 and CH4, and the average homogenization temperature from Ⅰ stage to Ⅲ stage is 189, 157, and 137 ℃, respectively; The average w(NaCleq) is 6.01%, 4.18%, and 2.01% in sequence. The initial ore-forming fluid is characterized by H2O-NaCl system fluid with medium-low temperature, low salinity, low density and contains volatile components such as CO2, N2 and SO2. In the early stage of mineralization, the hot brine in the basin with medium-high temperature and reducibility had a strong water-rock reaction with the surrounding strata, activating and migrating Au and S; In the main metallogenic period, the ore-forming fluid continuously flows upward driven by abnormally high pressure and faulting activities, and reacts with Fe and other elements in dolomite to form pyrite and arsenopyrite. At the same time, it mixes with atmospheric precipitation, the temperature and salinity drop rapidly, and Au and other ore-forming elements are unloaded in large quantities. In the late stage of mineralization, the ore-forming elements in the fluid were consumed, the atmospheric precipitation continued to mix in, the temperature and salinity dropped significantly, and the mineralization ended. The mineralization mechanism is fluid mixing and water-rock reaction.

Key words: fluid inclusion, source of ore-forming fluid, deposit genesis, Jinya Carlin-type gold deposit, Yunnan-Guizhou-Guangxi “Golden Triangle”