High salinity fluid characteristic and evolution of Xiaojiayingzi Mo (Fe) deposit, Liaoning province

Xiaojiayingzi Mo ( Fe) deposit is temporally and spatially associated with intermediate to mafic rocks and the mineralization hosted in skarn. Fluid inclusion studies show that two types of primary fluid inclusion occur in calcite and quartz from molybdenite mineralization stage; daughter crystal-bearing polyphase inclusion and aqueous two-phase inclusion. The former homogenized to liquid phase by dissolution of daughter minerals, with homogenization temperatures from 203 to 440°C and salinity ranging from 32. 0% to 52. 0% NaCl equiv. The latter homogenized to the liquid phase by disappearance of the vapor bubble at homogenization temperatures from 146 to 340°C , salinity between 4.3% to 18.4% NaCl equiv. The fluid inclusion in granet and chondrodite from garnet skarn stage and magnetite mineralization stage are mainly of daughter crystal-bearing polyphase, which homogenized to the liquid phase by disappearance of vapor phase and homogenization temperatures from 505 to 560°C and 435 to 541°1, salinity from 43. 4% to 50. 0% NaCl equiv and 44. 9% to 56. 9% NaCl equiv, respectively. Fluid inclusion and H-0 isotope analysis show that the ore-forming fluid from pre-ore stage is characterized by high temperature and high salinity. The high temperature and high salinity fluid came from magmatic hydrothermal fluid during the decreasing of pressure and temperature. The ore-forming fluid from molybdenite mineralization stage are characterized by mixed fluid of high temperature and high salinity fluid end and medium to lower temperature and lower salinity fluid end. During the evolutional processes of ore-forming fluid, the transformed of the pressure and density of high temperature and high salinity fluid play an important role to magnetite minealization, and the mixing of fluid between high salinity and lower salinity take a positive influence to molybdenite deposition.