Comparisons of the fluid inclusions in the main types of gold deposits in Jiaodong area and the indication on their metallogenic conditional differences: a case study of Shaling, Jiudian and Liaoshang gold deposits

Jiaodong area is the most important gold ore-concentrating area in China.The altered-rock-type in fractured zone, quartz-vein-type and pyrite-carbonate-vein-type gold deposits are the main mineralization types.Previous studies on the differences of mineralization conditions of different mineralization types are still lacking.Fluid inclusions of three typical gold deposits in Jiaodong are studied in this paper.The fluid inclusions of gold deposits of different mineralization types have similar petrographic characteristics in main mineralization stages.There are four types of fluid inclusions, including H₂O-CO₂(Ⅱ-g type), CO₂-rich(Ⅲ_CO2 type)and aqueous solution inclusions(Ⅰ-l type and Ⅱ-l type), which belong to CO₂-H₂O-NaCl±CH₄ system.The fluid inclusions of pyrite-carbonate-vein-type gold deposit are obviously different from other types of mineralization due to higher salinity and homogenization temperature.The fluid inclusions of quartz-vein-type gold deposit are different from altered-rock-type gold deposit in fractured zone due to larger diameter and higher proportion of three-phase inclusions.The ore-forming fluid of altered-rock-type and quartz-vein-type gold deposits are belong to medium-low temperature, salinity and low density fluid as a whole, while the pyrite-carbonate-vein-type gold deposit belongs to medium-high temperature, medium-low salinity and low density fluid.The study of fluid inclusions in the ore-body at -1000 ~ -2000 m depth in the Shaling gold deposit show that the ore-forming fluids have the same characteristics except the salinity decrease in the vertical depth of 2000 m, indicating that ore-forming fluids at different depths have the same properties and physicochemical conditions.The general consistency and partial difference of the fluid characteristics of different gold deposits indicate that the Jiaodong gold deposit was formed in a short time under a unified metallogenic structure-fluid background in different local environments.