Abstract:

Studies on the primary fluid inclusions in quartz of tourmalite from exhalative sedimentary process in Houxianyu borate deposit and in quartz vein from epigenetic hydrothermal activity in Wengquangou borate deposit  in eastern Liaoning Province were carried out. The results indicate that there are only twophase primary aqueous inclusions in quartz of tourmalite from Houxianyu borate deposit. Micro-thermometric studies show that the data of  homogenous temperature range from 146 ℃ to 249 ℃, with salinity from 15.9% to 18.4%(NaCl equivalent),and density from 0.96 g/cm³ to 1.04 g/cm³. The ore-forming pressures obtained from the fluid inclusion study range from 43.95 MPa to 68.43 MPa. The depths of sea water range from 4.40 km to 6.84 km based on the pressures when exhalative sedimentary process occurred. The results on the basis of gas component analysis show that the ore-forming fluids are mainly composed of H₂O and CH₄, with a certain amounts of CO₂, N₂ and minor amounts of H₂S and H₂. The fluid inclusions in quartz vein from Wengquangou borate deposit can be classified into twophase aqueous type and CO₂-bearing three-phase type. Micro-thermometric studies indicate that the data of homogenous temperature, salinity and density vary from 142 ℃ to 377 ℃, 12.7% to 14.5%(NaCl equivalent), and 0.96 g/cm³ to 1.01 g/cm³, respectively. The ore-forming pressures range from 43.48 MPa to 65.86 MPa. The forming depths of epigenetic quartz vein range from 5.23 km to 6.55 km. The results on the basis of gas component analysis show that the fluids are mainly composed of H₂O and CO₂, with a certain amounts of CO, N₂, H₂, minor amounts of CH₄ and H₂S and trace amounts of C₂H₆. The geological characteristics of the two deposits and their boron isotopic compositions show that both deposits are exhalative sedimentary deposits, and undergone regional metamorphic reconstruction and hydrothermal alteration. The characteristics of fluid inclusions show that exhalative sedimentary process occurred in relatively deoxidized ocean  floor environment, while epigenetic hydrothermal activity occurred in relatively oxidative one.

Key words: borate deposit, fluid inclusion, Houxianyu, Wengquangou, eastern Liaoning Province