Characteristics Of Ore-forming Fluids And Evolution On The Pb, Zn Ore-concentrated Area In Qingchengzi Region, Liaoning Province, China

Qingchengzi ore concentration area in Liaoning province is a significant Pb-Zn polymetallic ore field on Eastern Liaoning-Southern Jilin Metallogenic Belt.Rock masses outcropped in the Qingchengzi ore concentration area mainly include Proterozoic Dadingzi,Indosinian Xinling and Shuangdinggou,Yanshanian Yaojiagou;main deposits occurred in this area are Xinling molybdenum,Yaojiagou molybdenum,Zhenzigou-type stratiform lead-zinc,Zhenzigou-type vein lead-zinc,Gaojiapuzi cataclastic marble silver and Gaojiapuzi independent silver ores.Main mineralizing stage’s fluid inclusions of Xinling molybdenum ore mainly belong to liquid-rich phase,vapor-rich phase,three phases containing CO₂,one containing daughter mineral and pure CO₂.Fluid inclusions’homogenization temperatures concentrate between 280and 420℃,salinities converge in two ranges respectively,i.e.4-14 wt%and 42-56 wt%,densities centralize between 0.65 and 0.90 g·cm-3,and matollogenic pressure focus between 90and 130 Mpa.Main mineralizing stage’s fluid inclusions of Zhenzigou-type vein lead-zinc ore mainly include liquid-rich phase,vapor-rich phase and three phases containing CO₂,and a inclusion containing daughter mineral was also found.Fluid inclusions’homogenization temperatures concentrate between 220 and 340℃,salinities converge in 4-10 wt%,densities centralize between 0.80 and 0.90 g·cm^-3,and matollogenic pressure focus between 80 and 210 Mpa.Main mineralizing stage’s fluid inclusions of Gaojiabaozi cataclastic marble silver ore are basically liquid-rich phase,vapor-rich phase and three phases containing CO₂.Fluid inclusions’homogenization temperatures concentrate within two ranges respectively,i.e.160-200℃and300-340℃,salinities converge in 2-6 wt%,densities centralize between 0.90 and 0.95 g·cm^-3,and matollogenic pressure focus between 100 and 130 Mpa.Main mineralizing stage’s fluid inclusions of Yaojiagou molybdenum ore mainly fall within liquid-rich phase,vapor-rich phase,three phases containing CO₂ and pure CO₂.Fluid inclusions’homogenization temperatures concentrate between 280 and 380℃,salinities converge in 4-12wt%,densities centralize between 0.65 and 1.12 g·cm^-3,and matollogenic pressure focus between 124 and 180 Mpa.Main mineralizing stage’s fluid inclusions of Gaojiabaozi independent silver ore predominantly involve liquid-rich phase and vapor-rich phase.Fluid inclusions’homogenization temperatures concentrate between 130 and 170℃,salinities converge within 2-6 wt%,densities centralize between 0.9 and 1.01g·cm^-3,and matollogenic pressure focus between 88 and 155Mpa.According to the results above,from Xinling rock mass located at center to circumjacent Xinling molybdenum,Zhenzigou-type vein lead-zinc and Gaojiabaozi cataclastic marble silver ores,metallogenic fluid’s homogenization temperatures,salinities of the Indosinian deposits regularly exhibit the declining evolutional characteristics,and their diagenetic and metallogenetic ages are basically consistent,therefore they provide evidence on fluid aspect for classifying these deposits as the same metallogenic system.From Yaojiagou rock mass situated at center to ambient Yaojiagou molybdenum and Gaojiabaozi independent silver ores,metallogenic fluid’s homogenization temperatures,salinities of the Yanshanian deposits regularly show the decreasing evolutional pattern and their diagenetic and metallogenetic ages are nearly equal,thus they support to put these deposits under the same metallogenic system on the basis of the evidence from fluid aspect.