Geology And Ore-forming Fluid Of Silver-Lead-Zinc Lode Deposit Of Shagou, Western Henan Province

Shagou vein-type Ag-Pb-Zn ore deposit in the south margin of North China Craton is composed of vein and replacement ore types. The main Shagou vein presents a paragenesis that can be divided into four stages: (a) an early quartz-pyrite stage, (b) a sphalerite-galena-quartz-minor silver minerals stage, (c) a galena-quartz- sphalerite-silver minerals, and (d) a late calcite-quartz stsge.Quartz Q1 of the first paragenetic stage contains two (LV) and three phase (LVH) fluid inclusions. These two fluid inclusion types are interpreted as the result of trapping of a salt-saturated fluid with a salinity between 6.45 and 11.10 wt. % NaCl equiv. Such high salinities are probably due to sudden decompression of the fluid exsolved by the magma. Primary two (LV) fluid inclusion in Quartz Q₂ from the first stage homogenize at temperatures between 285～360℃, with a average of 325℃. Isotopic compositions of the fluid associated with the Quartz Q₂ define a trend with constantδ¹⁸O andδD values(δ¹⁸O_H2O=-7.8～9.5‰V-SMOW andδD=--96～-84‰V-SMOW), which is interpreted as magmatic component.Primary two (LV) fluid inclusions from the second stage homogenize at temperatures between 185～357℃, with salinities ranging between 4.65 and 10.11 wt.% NaCl equiv. Primary two (LV) fluid inclusion from the third stage homogenize at temperatures between 145～288℃, with salinities ranging between 1.91 and 10.86 wt. % NaCl equiv. This two stages bear isotopic characteristics defining a trend with a couple increase ofδ18O andδD(δ¹⁸O_H2O=-0.3～4.2‰V-SMOW andδD=-88.8～-59.8‰V-SMOW) and is explained by addition of meteoric water to the system.Primary two (LV) fluid inclusion from the third stage homogenize at temperatures between 129～208℃, with salinities ranging between 1.40 and 4.03 wt. % NaCl equiv. This late stage bear isotopic characteristics defining a trend with a couple increase ofδ¹⁸O andδD(δ¹⁸O_H2O=-2.7～-0.1‰V-SMOW andδD=-73～-60‰V-SMOW) and is explained by addition of more meteoric water to the system.Based on the ore-forming fluid, Shagou Ag-Pb-Zn ore deposit is related with the fluid exsolved by the magma.