EXPERIMENTAL MODELING OF THE TRANSFORMATION OF H2 O-CO2-CH4 INCLUSIONS DURING ISOBARIC COOLING AND ISOTHERMAL COMPRESSION

Abstract

The transformations (density, composition, or shape alterations) of fluid inclusions under isobaric cooling and isothermal compression have been experimentally modeled. The H2O-CO2 -CH4 inclusions used in the model experiments have been synthesized in quartz at 1 or 3 kbar and 700°C. The parameters of the model experiments were as follows: for isobaric cooling, 700-400°C at 1 or 3 kbar; for isothermal compression, 1-3 and 3-5 kbar at 400 and 700°C, respectively. The shape of the inclusion walls changed as a result of the experiments because of the dissolution and reprecipitation of the host phase. The intensity of these changes was directly affected by the pressure and temperature differences and the amount of the aqueous phase in the inclusions. Fluid densities increased in many inclusions in the run products: the increase ranged from insignificant (0.06 g/cm3) to fairly noticeable (0.15 g/cm3). The composition of the fluid inclusions also changed. The results of the experiments, in particular of those carried out with a labeled fluid, show that the penetration of a denser external fluid into inclusions with a lower fluid density is the basic reason for the increase in the density and change in the composition of fluid inclusions. In several experiments, the methane concentration changed with an attendant change in the melting temperature of carbon dioxide but without noticeable changes in the carbon dioxide homogenization temperature. © Pleiades Publishing, Inc. 2006.