Cryogenic Raman Spectroscopic Studies on Common Ore-forming Fluid Systems

The composition and properties of ore-forming fluids are key to understanding the mechanisms of mineralization in ore deposits. These characteristics can be understood by studying fluid inclusions. Hydrates in fluid inclusions containing NaCl-H2O and MgCl2-H2O were studied using cryogenic Raman spectroscopy. The intensity ratio of peaks at 3401, 3464, 3514, and 3090 cm(-1) shows a positive correlation with the concentration of hydrates in the inclusions, as does the ratio of the total integrated area of the MgCl2 hydrate peak (3514 cm(-1)) to the 3090 cm(-1) peak with the concentration of MgCl2 (correlation coefficient >0.90). These correlations are important in the quantitative analysis of MgCl2 in synthetic and natural NaCl-MgCl2-CaCl2-H2O-bearing fluid inclusions. Semi-quantitative analysis of NaCl-MgCl2-H2O solutions indicates that peaks at 3437 and 3537 cm(-1) reflect the presence of NaCl in the solution. Further, a peak at 3514 cm(-1) is indicative of the presence of MgCl2. The relative intensities of these peaks may be related to the relative abundances of NaCl and MgCl2. A quantitative attempt was made on NaCl-MgCl2-CaCl2-H2O system, but it was found that quantifying NaCl, MgCl2 and CaCl2 separately in NaCl-MgCl2-CaCl2-H2O system by the secondary freezing method is difficult.