Abstract:

The Dayinjian Mo deposit, as an important deposit in the Dabieshan Mo-polymetallic belt, has genetic links to monzogranite intrusion of Late Yanshanian, and has attracted extensive attention for great progress in recent exploration. Based on the petrography and microthermometry of fluid inclusions in the quartz veins formed in main mineralization stage, 4 types of primary fluid inclusions were identified, including: (1) aqueous-rich two-phase inclusions (L-type), (2) vapor-rich two-phase inclusions (V-type), (3) daughter mineral-bearing three-phase inclusion (S-type) and (4) CO2-bearing three-phase inclusions (C-type), The analysis results indicate that two main homogenization temperatures present at 280~320 ℃ and 200~220 ℃, respectively, while the salinities range in two intervals of 5.11%~9.98% (NaCleq) and 36.06%~42.78%(NaCleq), respectively. The densities of the trapped fluids vary from 0.91 g/cm3 to 1.10 g/cm3. Raman spectra of the inclusions indicate that water vapor is the dominant component with minor amount of CO2 (possibly a little N2 in some cases) in the gasous phase of the inclusions. The typical shift in oxygen isotope compositions suggests a mixing event between magmatic and meteoric water. In summary, the deposit is an intermediate-high temperature epithermal deposit, and the fluid mixing plays crucially significant roles in the mineralization.

Key words: fluid inclusion, microthermometry, Raman spectroscopy, hydrogen and oxygen isotopes, Dayinjian Mo deposit, Dabieshan orogen