The fluid inclusions, H-O-C-S-Pb isotopic characteristics and genesis of the Liaoshang gold deposit in Jiaodong Peninsula

The Liaoshang gold deposit is located in the northeastern margin of the Jiaolai Basin.It is the only super-large gold deposit in the eastern part of the Jiaodong Peninsula.This paper discusses the genesis of the Liaoshang gold deposit through fluid inclusions and H-O-C-S-Pb isotopic geochemistry.The fluid inclusions in the main ore-forming stage have a completely uniform temperature range of 125~345℃, the main metallogenic temperature range of 260~320℃, salinity of 2.22%~13.87%NaCl_eqv, and fluid density of 0.68~1.02 g/cm³, indicating that the ore-forming fluid is a reductive hydrothermal system with medium-low temperature, medium-low salinity, low density, and rich in CO₂. H and O isotopes(δD=-82.6‰~-68.9‰, δ¹⁸O_W-SMOW=0.24‰~+3.33‰) and fluid inclusion composition indicate that the ore-forming fluid is a mixed fluid of mantle hydrothermal fluid and magmatic hydrothermal fluid + atmospheric precipitation.The carbon and oxygen isotope composition(δ¹³C_PDB=-2.9‰~-4.7‰, and δ¹⁸O_SMOW=6.9‰~9.6‰, ) indicate that C in the ore-forming fluid originated from the granite source area.The δ³⁴S of the ore ranges from 7.6‰ to 12.6‰.²⁰⁶Pb/²⁰⁴Pb ratios ranging from 17.202 to 17.955, ²⁰⁷Pb/²⁰⁴Pb ratios ranging from 15.457 to 15.577, and ²⁰⁸Pb/²⁰⁴Pb ratios ranging from 37.729 to 38.341, indicate that the lead source is the Early Cambrian metamorphic rock series mainly from the lower crust, mixed with mantle-derived lead.Studies indicate that the Liaoshang gold deposit is a magmatic hydrothermal gold deposit related to the Early Cretaceous Weideshan-type granite.The mixture of magmatic hydrothermal fluids related to the activity of crust-mantle mixed granite magma, mantle fluids and atmospheric precipitation produced fluid immiscible mineralization under the effect of heat uplift-extension structure.