岡山大学温泉研究所 Acta Medica Okayama 0369-7142 40 1971 温泉の同位体的研究I 温泉水の酸素の同位体比の測定について 33 40 EN Osamu Matsubaya Hitoshi Sakai Hinako Tanaka Tazue Uemura The CO(2)-H(2)O isotopic equilibration technique was studied for the routine analyses of the oxygen isotopic ratios of hot spring water. A reaction vessel containing 2 ml of water and 0.16 m mole of tank CO(2) was shaken for 18 hrs. in a constant-temperature bath at 25.0℃ (Figs. 1, 2, and 3), and the CO(2) was analyzed for the oxygen isotopic ratio by a MCKINNEY type mass spectrometer. Several aliquots of 1, 2 and 5 ml from a same water were each analyzed three times by successive equilibration (Table 1). The observed values differ depending on the volume of water but the corrected values by equation (6) indicate excellent agreement, implying the whole processes to be well controlled. The reproducibility of the isotopic analyses is better than ± 0.1‰ (Table 2) in most cases, and the accuracy would not be worse than ± 0.2‰ as demonstrated by the interlaboratory comparison of some standard samples (Table 3). Oxygen isotopic ratios of water from more than 70 hot springs in Japan are presented (Table 5). Although the results will be discussed in the following issues of this series of paper, most hot spring water have the δ(18)O values similar to those of meteoric waters in Japan. However, spring water from Arima Hot Springs, Hyogo-Pref., which has been known by its abnormally high chloride and low sulfate concentrations is of an exceptionally high δ(18)O value. No potential conflict of interest relevant to this article was reported.

岡山大学温泉研究所 Acta Medica Okayama 0369-7142 45 1976 Oxygen Isotopic Data and Description of Rocks of the Yanai District in the Ryoke Belt, Japan 69 73 EN Hiroji Honma Hitoshi Sakai No potential conflict of interest relevant to this article was reported.

岡山大学温泉研究所 Acta Medica Okayama 0369-7142 43 1974 有馬地域の温泉,鉱泉の水素と酸素の同位体比について 15 28 EN Osamu Matsubaya Hitoshi Sakai Michiji Tsurumaki Saline waters of thermal and mineral springs in Arima area, at Takarazuka, and in Ishibotoke area of Kawachinagano City indicate wide ranges of δD and δ(18)O values (Table 1). Excellent linearity exists between the δD and δ(18)O values (Fig. 1) and between the δ(18)O value and the chloride concentration (Fig. 2). These facts as well as the chemical evidence of the previous investigators strongly support the view that Arima springs are admixtures of a single deep brine and local ground water (TSURUMAKI, 1964). The deep brine may have the δ(18)O value of +8.0〜+8.5‰, the δD value of -25〜-30‰, and the chloride concentration of 1.20〜1.25 eq/l, which were estimated from the water of the maximum salinity so far reported. Because the thermal and mineral springs in Arima area closely associate with the upper Cretaceous granitic rocks, and the estimated δ(18)O value of the deep brine is similar to a value of water in isotopic equilibrium with those granitic rocks at 500〜600℃, the deep brine of Arima might have been the magmatic water of those granitic rocks. The mineral springs at Takarazuka and in Ishibotoke area also show the similar linearity among Cl(-), δ(18)O and δD to those in Arima area. Therefore it is assumed that the mineral springs at Takarazuka may be of the same origin as that in Arima area, and the mineral springs in Ishibotoke area might have been the fluid associated with Ryoke metamorphic rocks. Alternatively, the deep brine in Arima area may be isotopically and chemically similar to the saline formation waters in Illinois basin (GRAF et al., 1966). The high δD values and salinities of those formation waters were attributed to the isotopic and chemical fractionation during the passage of water through sediments. The deep brine in Arima area may be genetically similar to those saline formation waters. If such a saline water could have formed in Osaka basin, it is not surprising to find out the similar brines at Arima and Ishibotoke which are the northwestern and southeastern rims of the basin, respectively. At the present, it cannot be answered which of these two models is more probable. Further studies on other saline springs fluid inclusions of Cretaceous granitic rocks may be useful in order to solve this problem. No potential conflict of interest relevant to this article was reported.

岡山大学温泉研究所 Acta Medica Okayama 0369-7142 47 1978 北海道の温泉ならびに火山についての同位体化学的調査報告 55 67 EN Osamu Matsubaya Hitoshi Sakai Akira Ueda Makoto Tsutsumi Minoru Kusakabe Akira Sasaki Stable isotope ratios of hydrogen, oxygen, carbon and sulfur of precipitation, thermal and mineral waters, and volcanic gases were measured. The isotopic data combined with chemical and geological information were discussed in terms of origin and evolution of the hotsprings and volcanic gases. The hotsprings along the Uchiura Bay, Oshima Peninsula are mostly near-neutral NaCl-type thermal water and may be divided into three groups : (1) thermal waters isotopically similar to the precipitation of this area, (2) those similar in D/H to the local meteoric waters but enriched by 2 to 3‰ in (18)O compared to the latter, and (3) those enriched significantly in both D and (18)O relative to the local meteoric waters. The first and second types of thermal water probably form from local meteoric water which percolates through "Green Tuff" formations and acquires dissolved chemicals from them. However, high salt concentration and the oxygen isotope shift (thesecond type) may imply that the NaCl-type water of volcanic origin might be involved. On the other hand, the waters of the third group can be explained by mixing of modern sea water into the second type thermal water (in case of Yachigashira) or by incorporation of fossil sea water of Tertiary origin into modern meteoric water (Nigorigawa). Except for Esan, Noboribetsu and Atosanupuri volcanic systems, waters from all the hotsprings and volcanic fumaroles associated with Quaternary volcanic rocks are meteoric in origin. Thermal waters at Esan, Noboribetsu and Atosanupuri have δD = -30〜-50 and δ(18)O = -1〜+ 3‰ and are enriched in D and (18)O relative to local meteoric water of the respective area. The origin of these waters and the mechanism (s) controlling the isotope ratios could not be made clear by the present study. Interesting is the finding that at Esan, Noboribetsu and Atosanupuri, thermal waters are enriched in D and (18)O relative to near-by fumarolic gases. The enrichment factor is 18 to 26‰ for hydrogen and 4 to 6‰ for oxygen, implying that more than one stages of liquidvapor separation are taking place in underground hydrothermal systems. No potential conflict of interest relevant to this article was reported.

岡山大学温泉研究所 Acta Medica Okayama 0369-7142 50 1980 長野県の温泉についての同位体化学的調査報告 17 24 EN Osamu Matsubaya Hitoshi Sakai Minoru Kusakabe Akira Sasaki Water samples from 28 hotsprings and mineral springs in Nagano Prefecture, central Japan, were examined for their stable isotope ratios of hydrogen, oxygen, carbon, and sulfur. Spring waters of Kashio are highly saline and enriched in heavy isotopes of oxygen and hydrogen (δ(18)O=-2.5〜-4.6‰, δD=-54〜-57‰). Linear relationships among δD, δ(18)O, and Cl(-) suggest that spring waters are the mixtures of a deep brine and local surface water. Extrapolation of the linear relationships indicates that the deep brine is both isotopically and chemically very similar to the deep brine previously suggested for the springs of Arima, Takarazuka, and Ishibotoke of which δD, δ(18)O, and Cl(-) are estimated as -33‰, +8.0‰, and 44g/l, respectively. A common origin may be warranted among these postulated brines, while their provenance is yet to be worked out. The hot springs in Matsushiro are a Na-Ca-Cl type of high carbonate content. Their hydrogen and oxygen isotope ratios (δD=-71〜-46‰, δ(18)O=-9.1〜-2.0‰) are higher than the local surface water. On the basis of the relationships among δD, δ(18)O, and Cl(-), they are considered to be the mixtures of fossil sea water and certain water of meteoric origin of which Cl(-) is about 4g/l and δ(18)O is higher by about 3‰ than the local surface water. The latter may be meteoric water circulating in the marine sedimentary formations (Green Tuff formations) with soluble sea salts. Isotopic exchange with carbonate minerals in the formations explains its (18)O enrichment. Spring waters from Yashio and Isobe (Gunma Pref.) as well as Yunosawa and Yatate (Akita Pref.) were previously interpreted to be mixtures of fossil sea water and local surface water of low Cl(-) content. Re-examination of their data revealed that the meteoric waters responsible for these springs contain about 3g/l Cl(-), similar to the value obtained for Matsushiro. However, unlike Matsushiro, the meteoric waters in these areas are found to be isotopically similar to the local surface waters. Waters from other hot springs studied here are of simply meteoric origin, thus belonging to the GreenTuff type water previously defined. No potential conflict of interest relevant to this article was reported.

岡山大学温泉研究所 Acta Medica Okayama 0369-7142 50 1980 400℃, 1000気圧の熱水中におけるSO(2-)(4)-H(2)S間のイオウ同位体交換反応の実験的研究 1 15 EN Emi Kamada Hitoshi Sakai Noriaki Kishima Experimental procedures used in this study are the same as those developed by Sakai and Dickson (1978). 0.005 M Na(2)S(2)O(3) solutions were heated to 400℃ under 1000 bar water pressure in a gold bag of Dickson gold-bag equipment (Fig. 1). At an elevated temperature Na(2)S(2)O(3) quickly and completely decomposed into 1:1 mixture of SO(4)(2-) and H(2)S (eq. (1)) and subsequent isotope exchange (eq. (2)) was monitored by consecutively withdrawing aliquots of solution for chemical and isotopic analyses at desired time intervals. For the preparation of SO(2) for isotope analyses, 2 to 5 mg BaSO(4) was thoroughly mixed with silica glass powder of 10 times the BaSO(4) in weight and heated to 1400℃ or so in sealed, evacuated silica glass tubings (see Fig. 2 and equation (4)). The technique is a modification of Holt and Engelkemeir (1971). The (18)O/(16)O ratios of SO(2) thus formed stayed constant by exchange with silica glass powder (Fig. 3). Numerical data of the three runs performed in this study are summarized in Tables 1 to 3. In runs 2 and 3, a small aliquot of (34)S- enriched H(2)SO(4) was added into the starting solution and thus equilibrium was approached from above the quilibrium value (see Fig. 4). When isotope exchange occurs between two molecules, X and Y, the reaction rate, r, is related to the extent of exchange, F, at given time, t, by equation (17), where X and Y indicate concentrations of given species, α(e), α(o) and α denote the　fractionation factor at equilibrium, at time　t=0 and at an arbitrary time t, and F = (α - α(o))/(α(e) - α(0)) or the extent of isotope exchange. Assuming the exchange rate is of the first order with respect to both X and Y and to the β'th power of hydrogen ion activity, a(H)(+), eq. (17) reduces to eq. (19), where k(1) denotes the rate constant. If X, Y and pH of solution stayed constant during the run, the half-time, t(1/2), of the exchange reaction can be obtained graphically as shown in Fig. 5. The t(1/2) for runs 1, 2, and 3 are determined to be 5.8, 5.5 and 6.1 hrs, respectively. Introducing F=0.5 and t=t(1/2) into eq. (19), we obtain eq. (20) which is graphically shown in Fig. 6 using the data by the present work and those by Sakai and Dickson(1978). The numerical values of log k(1) + 0.16 may be obtained by extrapolating the lines to pH=0 and, from these values, the rate constant, k(1) , may be calculated for temperatures of 300° and 400℃. From these two values of k(1) and from the Arrhenius plot, the activation energy of the exchange reaction was calculated to be 22 kcal/mole, a much smaller value than 55 kcal/mole obtained by Igumnov (1977). The value of β is found to be 0.29 at 300℃ and 0.075 at 400℃, although the physico-chemical nature of β is not clear to the present authors. Using these values, eq. (24), where C is a constant, is derived which would enable us to calculate the t(1/2) of any system of known ΣS and pH. However, as we do not know yet how β varies with different systems, eq. (24) is applicable only to limited systems in which temperature, total sulfur contents and pH are similar to those of the present study. Fig. 7 illustrates how t(1/2) varies with pH and total sulfur content at 300° and 400℃ and predicts t(1/2) for some solutions obtainable by hydrothermal reactions of seawater with various igneous rocks. The average equilibrium fractionation factor at 400℃ obtained by this study is 1.0153, in good accord with 1.0151 given by Igumnov et al. (1977). Theoretical fractionation factors between SO(4)(2-) and H(2)S have been calculated by Sakai (1968) , who gives too high values compared to the experimental data obtained by this and other researchers (Fig. 9). In the present study, the reduced partition function ratio (R.P.F.R.) of SO(4)(2-) was recalculated using two sets of the vibrational frequencies of SO(4)(2-) (shown in Table 5) and the valence force fields of Heath and Linnett (1947), which reproduces the observed frequencies of SO(4)(2-) better than Urey-Bradley force field used by Sakai (1968). The results of new calculation are shown in Table 6. This table also includes the R.P.F.R. of H(2)S which was calculated by Thode et al. (1971). Using these new R.P.F.R. of SO(4)(2-) and H(2)S, the fractionation factors between SO(4)(2-) and H(2)S were calculated and are listed in the last column of Table 6 and plotted in Fig. 9. Fig. 9 indicates that the new calculation gives values more shifted from the experimental values than before. The major sulfate ions in our solution at 300° and 400℃ exist as NaSO(4)(-) (Sakai and Dickson, 1978; see also Table 4 of this paper) and, therefore, the measured fractionation factors are those between NaSO(4)(-) and H(2)S. The discrepancy between the theory and experiments may, at least, be partially explained by this fact, although other more important reasons, which are not known to us at the moment, may also exist. No potential conflict of interest relevant to this article was reported.

岡山大学温泉研究所 Acta Medica Okayama 0369-7142 53 1983 イオウ同位体比分析法の比較検討と同位体比標準物質の検討 77 84 EN Fumitaka Yanagisawa Tadashi Miyoshi Akira Ueda Hitoshi Sakai Three techniques (combustion of Ag(2)S by Cu(2)O, thermal decomposition of BaSO(4) and KIBA reagent method under vacuum) for sulfur isotope ratio measurements of geological samples are described in detail. The δ(34)S values of three working standards (MSS-2, MSS-3 and MSS-4) obtained by these techniques for the last 13 years were compared (Table 1 and Fig. 3): the most acceptable values of the three standards are +21.5, +3.5 and +4.5‰, respectively. No potential conflict of interest relevant to this article was reported.

岡山大学温泉研究所 Acta Medica Okayama 0369-7142 56 1985 水試料の敢素同位体比の自動測定 27 34 EN Hitoshi Chiba Hitoshi Sakai Masatoshi Yasutake The automatic sample preparation system for oxygen isotope analysis of natural water samples was constructed. The system is essentially a modification of that originally designed by W. Dansgaard in the University of Copenhagen. Sixty water samples of 5 ml each are automatically equilibrated with CO(2) of 30 ml NTP each within 4.5 hours. The equilibrated CO(2) gases are successively measured for their oxygen isotopic ratios by an automatic mas-sspectrometer, VG903. The time required for the measurement of the 60 CO(2) samples is about 15 hours; thus approximately 20 hours are required to complete the isotopic measurements of 60 water samples. The accuracy of the oxygen isotopic analyses is about 0.1%. The result of oxygen isotopic analyses by the automatic preparation system agrees with that of the conventional method within about +0.1%. The results indicate that the automatic preparation system is applicable for the oxygen isotope analysis of natural water samples. No potential conflict of interest relevant to this article was reported.