Characteristic of ore-forming fluids of vein-type copper deposits in the Jingbian area of Lujiang-Zongyang volcanic basin in Anhui Province and its implications for mineralization

The Lujiang-Zongyang volcanic basin in Anhui Province is one of the important ore cluster regions in the Middle-Lower Yangtze metallogenic belt, which hosts many vein-type copper deposits(points).In this study, four vein-type copper deposits at Zhangjiadian, Jingbian, Zhouwa and Huzhan in the Jingbian area were chosen to study the characteristics of ore-forming fluids in order to preliminarily understand the metallogenic mechanism of vein type copper deposits.The study shows that fluid inclusions in the deposits are dominated by two-phase gas-liquid inclusions,occasionally with gaseous inclusions and pure liquid inclusions, suggesting that fluid system belongs to a H₂O-NaCl system.The microthermomentric analyses of the fluid inclusions show that the ore-forming fluids are characterized by mediumtemperature(220～240 ℃), low-medium salinity(8wt%～20wt%)and low density(0.86～1.16 g/cm³), indicating that the ore-forming fluid experienced weak fluid-boiling. It can be concluded that mixing between magmatic water and meteoric water resulted in extraction, precipitation and enrichment of the ore-forming materials in the fractures of rock mass and country rocks, thus forming fault-controlled vein-type copper deposits.