A noble gas study including measurements of relative abundances and isotopic ratios of noble gases was carried out for gas samples collected from gas wells in the Carpathian Basin, Hungary. 3He/4He ratios in gases in which CO2 predominates were 2.6 to 5.5 × 10-6, in contrast to 0.42 to 0.62 × 10-6 of those in gases in which CH4 prevails. The strainer depth of the former wells is in the range from 1, 400 to 1, 438 m, and that of the latter is 860 to 1, 183m. Contribution of the mantle He to the helium in the CO2 gases estimated to be 19 to 42% and that to the helium in the CH4 gases to be 2.5 to 4.0%. The δ13C (PDB) value of CO2 with the high 3He/4He ratio was in the range from -6.2 to -5.2‰, suggesting high contribution of the mantle CO2. A high contribution of mantle-derived gases to the tectonically quiescent area can be related to the thin crust and high heat flow in this region. CH4 predominant gases seem to be derived from an environment rich in K, Th and U. No isotopic anomalies were found for Kr and Xe.
In order to extract fluid inclusions in minerals, a new type ball-mill made of Pyrex glass designed by Kita (1981) was used. Samples used in this study were hydrothermal vein quartz, fluorite and arsenopyrite. Under suitable conditions, gases in primary inclusions could be extracted with little contribution of secondary inclusions. The conditions found adequate for quartz and fluorite samples from the Takatori mine are as follows; 1) initial grain size of the sample is 6 ∼ 10 mesh, and the amount of sample is about 4g, 2) preheating temperature of sample is set at the filling temperature of primary inclusions, and the preheating period is more than 12h in vacuum, 3) the duration period of crushing using an alumina ball for 30 ∼ 60min is necessary, and 4) the duration of gas-recovery procedure for more than 3h with the heating of the mill at the same temperature of preheating is necessary for the recovery of gasses adsorbed on the powdered sample. For quartz and fluorite samples, isotopic compositions of extracted gases including H2O, CO2 and CH4 were reproduced well. The CO2/H2O ratio obtained for fluid inclusions in quarts from the Takatori tungsten mine, Japan, varied considerably according to the difference in the condition of ball-milling. For arsenopyrite sample the isotopic results were scattered widely because SO2 was evolved during crushing even at room temperature, which may be due to the reaction between arsenopyrite and H2O. When this method is applied to extracting fluid inclusions in minerals, the experimental conditions such as 1) and 2) should be changed depending on the nature of samples, especially the filling temperature of primary inclusions is important to set the preheating temperature. Disadvantages inherent in the ball-milling method are, 1) incomplete extraction of fluid inclusions and 2) the adsorption of gases onto the powder surface. The latter can be overcome by heating the powdered sample during the recovery process of gases, which was proven by the simulation test. As far as the isotopic compositions of H2O, CO2 and CH4 extracted from fluid inclusions are concerned, disadvantages given above have no effect on the result.
