Study of CO2-bearing Fluid Inclusions by Means of the Freezing Stage Microscope
1971 Volume 21 Issue 108 Pages 286-300
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1971 Volume 21 Issue 108 Pages 286-300
CO2-rich fluid inclusions in minerals were studied by means of the freezing method. When CO2-rich inclusions were cooled, liquid CO2 or CO2 gas hydrate appeared in them, and the volume of these phases was various according to the content of carbon dioxide. As the change of the CO2 hydrate which was formed in inclusions was comparable to the phase diagram of the H2O-CO2 system at low temperature, it was possible to infer the inside pressure of fluid inclusions and to calculate the approximate concentration of carbon dioxide from the data on the solubility of carbon dioxide in water and the pressure-temperature-density relation of carbon dioxide. The CO2-rich inclusions were found in quartz from the Ohtani and Kaneuchi mines, Kyoto Pref., Takatori mine, Ibaragi Pref., and Taishu mine, Nagasaki Pref. It is interesting that these ore deposits except that of the Taishu mine belong to the hypothermal tungsten quartz veins. In any case, however, CO2-rich inclusions were found as secondary inclusions, or as primary inclusions in rock crystals from druses. This fact will imply that CO2 has been concentrated in the late stage of mineralization of these ore deposits.
