The concentrations of ²¹⁰Pb and ²¹⁰Po in a total of 73 samples of individual rain and snow collected at Fayetteville (36°N, 94°W), Arkansas, were determined radiochemically during the period between October 1982 and January 1984. A clear seasonal pattern of variation of the ²¹⁰Po/²¹⁰Pb ratio in rain was observed: the ratio reaches a maximum during the months of November and December or January and February each year. The ²¹⁰Po/²¹⁰Pb ratio data obtained in our laboratories since 1971 were compared with the results of the studies on seasonal variation of the sulfate concentrations in the stratosphere reported by Sedlacek et al. (1983) and the following general trend was observed: the occurrence of a peak sulfate concentration in the stratosphere caused by a major volcanic eruption is followed by the occurrence of a peak ²¹⁰Po/²¹⁰Pb ratio in rain and snow samples collected several months later. Effect of the atmospheric injections of excess ²¹⁰Po from major eruptions of volcanoes located in Alaska, Aleutian Islands, Kamchatka and Kurile Islands can be seen more clearly at Seattle (47°N, 122°W), Washington, than at Fayetteville (36°N, 94°W), Arkansas.

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Chemical compositions of 96 natural gas samples from various locations and gas sources at 67 sampling sites in Japan were analyzed. A gas chromatograph system was developed for precise analyses of concentrations of N₂, CH₄, CO₂, O₂, Ar, He, Ne, H₂, C₂H₆ and H₂S. Overall analytical errors were estimated to be less than 5% for most samples. A sampling reservoir was newly designed in this work. Main components of natural gas samples were CO₂, N₂ and CH₄. Whereas N₂ showed positive correlations with ⁴He and ³He concentrations, CO₂ and CH₄ showed negative correlations with them. Either a mechanism of dilution of the N₂ gas enriched in magmatic He by CO₂ and/or CH₄, or of dissipation of CO₂ from magmatic fluid was suggested. Concentrations of Ar and Ne were high in N₂-rich gas samples. Ratios Ne/N₂ and Ar/N₂ imply the presence of N₂ of non-atmospheric origin. The close relationship between CO₂ discharge and volcanic activities was pointed out. A possible source of CO₂ is carbonates of sedimentary rocks from which CO₂ may be released either by pyrolysis or by decomposition due to magmatic activity. Nitrogen and CO₂ derived from oceanic sediments may be included in Japanese natural gases associated with subduction of a down-going slab.

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In the Hakone geothermal system a variety of waters including precipitation, surface water, ground water, thermal water and steam condensate were analyzed for δD and δ¹⁸O, dissolved sulfate and carbonate for δ³⁴S, δ¹⁸O and δ¹³C, and some sulfur-bearing gases for δ³⁴S. Fifteen samples were collected monthly to see if there is any monthly change in the isotopic composition of water. Except in precipitation and steam condensates, no significant monthly changes were observed. δ¹⁸O_SO4 and δ³⁴S_SO4 analyses indicate that surface oxidation of volcanic sulfur produces isotopically light sulfate in water occurring at relatively high elevations. Sulfate minerals in the basement rocks formed by the Miocene submarine volcanism are another source of dissolved sulfate in waters at lower elevations. CO₂ originally derived from decomposition of marine carbonate is suggested as a carbon source for dissolved bicarbonate at higher elevations, although contribution of organic carbon becomes significant in waters at lower elevations. In a δD versus δ¹⁸O plot, surface waters including precipitation and ground water lie on the line, δD = 8δ¹⁸O + 17. On the other hand, thermal waters lie on a regression line, δD = 2.1δ¹⁸O − 33.5. Around the intersect of the two lines, δD = -51 ‰ and δ¹⁸O = -8.5 ‰, there is a swarm of point for groundwaters. We call the ground water with δD = -51 ‰ and δ¹⁸O = -8.5 ‰ “representative” groundwater (RGW). From both chemical and isotopic view points, thermal waters are interpreted to be a mixture of RGW and high temperature dense steam (HTDS), the latter being ultimately evolved from hydrothermal interaction of RGW with rocks containing appreciable amounts of hydrous silicates. Values of δD and δ¹⁸O for HTDS have been interpreted to be a result of rock-RGW interaction with the rock/water weight ratio of about 10, on the basis of isotopic material balance in a closed system with the use of δD of hydrous silicates in rocks as well as δD and δ¹⁸O values of RGW. When the ratio of about 10 is compared with those of other geothermal areas, the Hakone geothermal system is rock-dominated. Interaction between meteoric water and rocks including hydrous silicates under a rock-dominated condition can account for both hydrogen and oxygen isotopic shifts found in thermal waters.

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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.

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Amino acids in solution are adsorbed by Miocene argillaceous rock fragments which contain clay minerals of mica-smectite mixed layer. The order of the adsorption is as follows; lysine > glycine > alanine > valine, leucine > aspartic acid. Since basic amino acids are selectively adsorbed in the rocks, the amino acid composition could not be an indicator for determining the depositional environment, contrary to the studies of Sasaki (1978, 1974).

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