1 EXPERIMENTAL MODELING OF “SUPERDENSE ” FLUID INCLUSIONS

The experiments of increasing fluid inclusions ’ density were done with quartz samples where the inclusions of H2O-CO2 composition were preliminarily synthesized at 700oC and 3 kbar. Oxalic acid has been used as a fluid source. The experiments were performed in platinum capsules at 400oC, 3 kbar and 700oC, 5 kbar during 7 days. Oxygen fugacity was supported by NNO buffer. Before and after the experiments the inclusions were studied under the microscope and analyzed using digital camera, video-and computer technique. Temperatures of homogenization (Th) and melting (Tm) of carbon dioxide were measured using Linkam heating-cooling stage (THMSG 600) with the working temperature range from-195 to 600oC. The accuracy of measurements was ±0.1ºC. Synthesized inclusions are mostly flat isometric, sometimes faceted to some extent, sometimes more volumetric and elongated. All of the obtained inclusions have decreased CO2 melting temperatures comparing to pure carbon dioxide (-56.6oC) (Table 1,2), what indicates a possible methane impurity. It is confirmed by the Raman spectroscopy data (IM&P SB RAS, Novosibirsk) in accordance to which methane content in carbon dioxide varies from 4.2 to 5.4 mol.%. Volume relationships of fluid phases (CO2/H2O) in the inclusions are 0.9/0.1 on the average. Under the conditions of isobaric cooling (400oC, 3 kbar) the most noticeable changes took place in tw