Fluid Inclusion Study Of The Liubagou Gold Deposit In Inner Mongolia

The Liubagou gold deposit, located at the south wing of Urals - Daqing complex anticline in the Inner Mongolia's north margin of North China Craton, is one part of metallogenic belt in the north margin of North China Craton, which is the late hydrothermal gold deposit related to the remelting magmatism. In order to be able to achieve an in-depth understanding on ore-forming fluid characteristics and metallogenic evolution mechanism of the Liubagou gold deposit, the works about the petrographic, microthermometry, laser raman spectroscopy and H-O isotopes of inclusions have been studying much systematically in this thesis.The results of both petrographic observations and microthermometry temperature indicated that, there mainly are the inclusions of L-V water, the ones of CO₂-H₂O three-phase, and the ones with multiphase daughter mineral-bearing in type. They are classed into the early quartz-feldspar stage, the quartz-pyrite-epidote phase, the quartz-polymetallic sulfide stage, and the late carbonate stage. And their homogenization temperatures of fluid inclusions are 330℃～480℃, 180℃～390℃, 190℃～340℃, and 120℃～210℃respectively, and the corresponding changes in salinity are 11.3～17.8wt% NaCl eq, 8.0～15.7wt% NaCl eq, 5.1～11.9wt% NaCl eq, and 1.9～8.8wt% NaCl eq separately. The ore-forming fluids belong to the NaCl-H₂O-CO₂ system with medium-high temperature, medium-low salinity and medium-density, and the ore deposit was formed in the medium-deep ore-forming environment (the ore-forming depth is 3.3～5.2km). The mineralization of the Liubagou gold deposit is a process about the gradual reduction of temperature and salinity, and the metallogenic temperature increasing from east to west. So, the boiling actions of this deposit and the CO₂-CH₄ fluids have played an important role in Au mineralization.The testing results of laser raman indicate that, the liquid composition of fluid inclusions is H₂O, and their vapor composition are mainly H₂O and CO₂ and contain a small amount of or some volume of N₂, H₂S, CH₄ and other volatile components.The studies of H-O isotopes show that the sources of ore-forming fluids mainly are the magmatic hydrothermal in the early mineralization stage, and the ore-forming temperature and pressure are decreasing gradually with the continuation of minearalizaiton process, as well as the ratio of precipitation.What's more, after having compared the characteristics of various ore-forming fluids in both the Liubagou gold deposit and the Hadamengou gold deposit, we found that they are very similar in the nature of ore-forming fluids. Therefore, they should have a sane source and evolution of fluids.