FLUID INCLUSION MICROTHERMOMETRY AND GAS CHEMISTRY IN GEOTHERMAL SYSTEM, JAPAN AND ITS APPLICATION FOR THE STUDY OF FLUID EVOLUTION - Energy Research Developments: Tidal Energy, Energy Efficiency and Solar Energy - page 156

CO 2 content in the reservoir fluid decreased more or less during progressing of the
exploitation of geothermal field.
1. Introduction
Fluid inclusions in mineral are undoubtedly most important geological material to study
physicochemical change of the reservoir fluid in geothermal field, because they contain
evolutional fluids at various stages till now in geothermal reservoir. From the point of view,
fluid inclusion studies have been widely used to interpret the thermal evolution of many of
the liquid-dominated geothermal fields (e.g. Shimazu and Yajima, 1973; Taguchi and
Hayashi, 1983; Takenouchi and Shoji, 1984; Muramatsu, 1984; Takenouchi, 1986;
Muramatsu and Komatsu, 1996; Browne et al., 1974; Roedder, 1984) and the vapor-
dominated geothermal fields (e.g. Sternfeld et al., 1983; Belkin et al., 1985; Moore and
Gunderson, 1995; Gianelli et al., 1997; Moore et al., 2000). On the other hand, although gas
chemistry of fluid inclusion is very important to interpret the fluid chemical evolution of
geothermal field, it has been scarcely reported because of difficulty of measurement for a
little gas content in fluid inclusions in mineral. In numerous methods developed for fluid
inclusion analysis (Roedder, 1984; Shepherd et al., 1985), quadrupole mass spectrometry is
one of most useful methods to measure gas chemistry of tiny fluid inclusion.
Figure 1. Location of Japanese geothermal fields in this chapter.