Determining Pressure with Daughter Minerals in Fluid Inclusion by Raman Spectroscopy: Sphalerite as an Example

Raman frequency of some materials, including minerals, molecules and ions, shifts systematically with changing pressure and temperature. This property is often used as a pressure gauge in high pressure experiments with the hydrothermal diamond anvil cell (HDAC). Since the system of fluid inclusion is similar to that of HDAC, it can also be used to determine the internal pressure of fluid inclusions. Sphalerite is a common daughter mineral. In this study, the frequency shift of the 350 cm(-1) peak of sphalerite has been studied from 296 to 523 K and from 0.07 to 2.00 GPa using the HDAC. The global slope of the isotherms (partial derivative V-350/partial derivative p)(T) is 0.0048 in the studied pressure range. No significant variation of the slopes with temperature has been observed. The correlation between the frequency shift of the 350 cm(-1) peak of sphalerite and pressure and temperature is constrained as P=208.33(Delta V-p)(350)+3.13T-943.75. This relationship may be used to estimate the internal pressure of the sphalerite-bearing fluid inclusions.