CO2-H2O-NaCl fluid inclusions: Determination of bulk Vm-X properties

摘要

Pore fluids dominated by CO2, H2O and NaCl are key players in many hydrothermal and metamorphic processes in the Earth's crust. However, the quantitative determination of the molar volume (Vm) and composition (X) of such fluids trapped in fluid inclusions has been problematic. Here we develop a method to determine the bulk Vm-X properties of a common class of CO2-H2O-NaCl inclusions that at laboratory temperature consist of saline aqueous liquid plus one or two carbonic phases. New Vm-X diagrams allow the bulk Vm-X values of individual inclusions to be estimated based on three measurements: the dissociation temperature of CO2-clathrate-hydrate, the homogenization temperature of the carbonic phases, and the volume-fraction of the carbonic phases measured in an optical spindle-stage at laboratory temperature.