摘要
The high-grade ores in No.2 mining area of the Gongchangling iron deposit have close genetic relationship with skarnoid consisting of garnet,amphibole,chlorite,suggesting significant correlation with the hydrothermal activity.According to mineral association of skarnoid as well as mineral intersection and metasomatism of skarnoid and high-grade ores,the ore-forming process of high-grade ores of No.2 mining area of the Gongchangling iron deposit is divided into the early hydrothermal metasomatism stage,the late hydrothermal metasomatism stage and the quartz vein stage.Through petrographic and microthermometric studies and Laser Raman spectroscopy of fluid inclusions from quartz of skarniod of the early hydrothermal metasomatism stage, quartz of the late hydrothermal metasomatism stage and quartz of the quartz veins stage,the authors have found that the fluid inclusions compositionally include liquid-rich,gas-rich and daughter mineral-bearing multiphase inclusions.Although the types of the fluid inclusions of the three stages are similar,there are significant differences in homogenization temperatures and salinities.The fluid inclusions of the early hydrothermal metasomatism stage quartz yielded homogenization temperatures of 340~398℃,salinities of 0.88%~6.3%and 33.5%~40.6%.The fluid of this stage is characterized by high temperature,low salinity and high content of CO2-CH4-H2O,mixed with the fluid of high salinity,high temperature and halite daughter minerals,with the formation of a lot of high-grade ores.The fluid inclusions of the late hydrothermal metasomatism stage quartz yielded homogenization temperatures of 230~280℃and salinities of 0.88%~4.96%.The fluid of this stage is characterized by low salinity,low temperature and low content of CO2-H2O±CH4,implying that this stage might have been a relatively important stage for the formation of high-grade ores.The fluid inclusions of the quartz vein stage quartz yielded homogenization temperatures of 150~180℃and salinities of 1.06%~2.07%. The fluid of this stage is characterized by low salinity,low temperature and the existence of CO2-H2O.