Synchrotron FTIR microscopy of synthetic and natural CO2–H2O fluid inclusions

Fluid inclusions provide a record of the physical and chemical composition of fluids that flow through the Earth's crust. Here, we describe a novel use of synchrotron Fourier Transform Infrared (FTIR) microscopy to map three parameters in individual fluid inclusions: (1) very low concentrations of CO2, (2) variations of the state of CO2 and (3) variations in water structure. The intensity of the synchrotron light source allows compositional mapping of individual fluid inclusions, which provides high-resolution images of the distribution of different CO2 and H2O species within individual inclusions. High resolution spectra of the CO2, recorded here for the first time in fluid inclusions, show the rotational lines of CO2 gas. The results reveal predicted as well as unexpected distributions of CO2 gas in the inclusions.