Fig. 11

Evolution of the intensity of the 960 cm⁻¹ Raman band assigned to Re–O vibrations in ReO₄ complexes in the Re-bearing systems as a function of density of pure H₂O fluid. In all systems except Na₂O–ReO₂–H₂O, isolated ReO₄ complexes are the only Re-bearing complexes in the fluid. This means that for those systems, the integrated area, normalized to the same Raman spectroscopic setup, are proportional to the ReO₄ abundance, keeping in mind, nevertheless, that the temperature range for the data shown in the figure is between 600 and 900 °C. The highest temperatures also correspond to the greatest H₂O density because the pressure also increases with increasing temperature and the H₂O density is more sensitive to pressure than temperature in the temperature and pressure ranges of the experiments. As discussed in the caption to Fig. 9, absent correction for temperature, the proportionality of integrated area and ReO₄ abundance in the fluid might carry on the order of a 10% uncertainty. Density of H₂O was calculated with SUPCRT92 (Johnson et al. 1992), modified as described by Foustoukos and Mysen (2012) for expansion of pressures beyond the 500 MPa limit in the original SUPCRT92. The Raman bands are normalized to the same slit widths and acquisition times