Abstract:

The Xinhualong molybdenum deposit, located in the eastern Jilin Province, is a newly discovered porphyry deposit. The orebodies are mainly hosted in granodiorite-porphyry. The hydrothermal ore-forming processes can be divided into five stages: quartz-disseminated molybdenite, quartz-stockwork molybdenite, quartz-pyrite-chalcopyrite, quartz-polymetallic sulfides, quartz-carbonate. Some conclusions have been drawn through petrographic observation of fluid inclusions in this deposit: there are mainly gas liquid two-phase (L+V) inclusions, subordinately pure gas (V) and pure liquid inclusions (L), and minor daughter minerals bearing multiphase inclusions (L+V+S). The homogenization temperatures of fluid inclusions regularly change from the early stage to the late stage. The homogenization temperatures and salinities of fluid inclusions ranges from 172-385 ℃, and from 8.51%-45.44％, respectively. The peak values of homogenization temperatures of fluid inclusions formed in different stages are separately 360-390 ℃, 270-350 ℃, 250-260 ℃, 220-230 ℃, 170-190 ℃. The homogenization temperatures of daughter minerals bearing inclusions mainly range from 272-385 ℃, salinities  from 35.79％-45.44％, and densities from 1.07-1.08 g/cm³ respectively. Gas liquid two-phase inclusions are mainly in ranges of 172-381 ℃, 8.51％-23.36％, and 0.7-0.99 g/cm³ respectively. Laser Raman spectroscopy of inclusions indicate that the gas components are CO₂, H₂O, N₂ and CH₄. Petrographic and microthermometric studies indicate that the ore-forming fluid of the first and the second stage, with high temperature, high salinities, CO₂-bearing, took place boiling. The fluid boiling resulted in CO₂ escaping, temperature decreasing and abundant metal sulfides precipitating. Moreover, data of oxygen and hydrogen isotope indicate that the ore-forming hydrothermal fluid was dominated by magmatic water with mixing of meteoric water in the later stage, and the mechanism for ore-metals precipitation is fluid-boiling.

Key words: fluid inclusion, mineralization, Xinhualong molybdenum deposit, ore deposits, Yanbian area