Determining phase volumes of mixed CO2-H2O inclusions using microthermometric measurements

A new graphical technique has been developed which permits the composition and volumetric properties of mixed CO2-H2O inclusions to be determined using microthermometric measurements. If the values of only two of the four variables of a mixed CO2-H2O inclusion are known, the values of the other two variables can be taken from a diagram depicting the relationships between all four variables. The diagram can be used to derive the volume fraction of the CO2 phase from measurements of the partial and total homogenization temperature. It can also be employed in the opposite sense for determining the theoretical homogenization temperature of an inclusion which decrepitates before reaching total homogenization, provided a good visual phase volume estimate is available. The graphical technique can also be applied to mixed CO2-H2O inclusions which contain ≤6 wt% NaCl.