Fluid Evolution and Ore Genesis of the Songjianghe Au Deposit in Eastern Jilin Province, NE China: Constraints from Fluid Inclusions and H-O-S-Pb Isotope Systematics

The medium-sized Songjianghe Au deposit is located in the southeastern part of Jiapigou-Haigou gold belt (JHGB) central eastern Jilin Province, NE China. mineralization primarily characterized by disseminated-style ores and hosted low-/medium-grade metamorphic rocks Seluohe Group. ore bodies are governed NNW-striking brittle-ductile structures spatially correlated with silicic sericitic alterations. Four alteration/mineralization stages have been distinguished: (I) Quartz-pyrrhotite-pyrite, (II) quartz-polymetallic sulfides, (III) quartz-pyrite, (IV) quartz-calcite. fluid inclusion (FI) assemblage quartz from Stage I comprises C1-type, C2-type, C3-type, VL-type FIs, total homogenization temperatures (Th-total) 292.8 to 405.6 °C salinities 2.8 9.3 wt% NaCl eqv. Quartz II (main stage) developed C2-, C3-, a Th-total 278.5 338.9 8.1 III coexisting C3- FIs quartz, 215.9 307.3 2.4 7.2 Only observed IV, 189.5 240.4 3.7 5.7 Laser Raman spectroscopic results demonstrated minor CH4 C-type Stages II. suggest that fluids may evolved medium-high temperature, low-salinity immiscible CO2-NaCl-H2O ± system low homogeneous NaCl-H2O system. Fluid immiscibility caused rapid drop pressure main trigger for gold-polymetallic sulfide precipitation. formed under 352–448 850–1380 bar pressure, based on isochore intersection inclusions. H-O isotopic compositions (Stage I: δ18Ofluid = 5.6 5.8‰, δD −96.2 −95.7‰; II: 4.2‰, −98.7 −89.8‰; III: 1.2 1.4‰, −103.5 −101.2‰) indicate hydrothermal dominated magmatic water early (Stages II) mixed meteoric since III. pyrite S-Pb isotope data (δ34S: −2.91 3.40‰; 206Pb/204Pb: 16.3270 16.4874; 207Pb/204Pb: 15.2258 15.3489; 208Pb/204Pb: 36.6088 36.7174), combined Pb intrusive wall (the Group) district, ore-forming materials at predominantly source affected contamination In accordance features geology, metals, geodynamic setting, belongs mesothermal vein deposit, which intermittent stage Paleo-Pacific plate subduction during Late Jurassic.