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Volume 20 (1986)
- Issue 6 Pages 261-
- Issue 5 Pages 213-
- Issue 4 Pages 159-
- Issue 3 Pages 111-
- Issue 2 Pages 61-
- Issue 1 Pages 1-
Volume 20, Issue 6
Displaying 1-5 of 5 articles from this issue
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Juske Horita, Sadao Matsuo1986 Volume 20 Issue 6 Pages 261-272
Published: December 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSBasic technique for the extraction and isotopic analysis of fluid inclusions in halite was investigated using synthetic single crystals of halite and three natural halite samples from China. Vacuum ball-mill, vacuum decrepitation and vacuum melting methods were examined for the extraction of fluid inclusions. Results of analyses on δD and δ18O of the water in fluid inclusions extracted by the ball-mill method from synthetic single crystals agreed with those of the mother solution from which the single crystals were formed. Although the δ18O value of the water extracted by the melting method agrees well with that of the mother solution, the δD value was about 7‰ more negative than that of the mother solution. There was a great difference in both δD and δ18O of the water extracted by the two methods applied to the identical natural halite samples; the melting method gave consistently more negative values for both δD and δ18O compared with those by the ball-mill method. The difference was interpreted as a result of the hydrolysis of NaCI with H2O combined with the formation of oxides of alkaline-earth elements in brine inclusions in natural halite samples in the process of the melting method. Although the melting method has an advantage of complete recovery of volatiles in halite samples, the chemical and isotopic compositions of volatiles can not be retained owing to a variety of thermal reactions which occur at high temperatures. It was concluded that the ball-mill method is much superior to the melting method in order to obtain isotopic and chemical information on fluid inclusions in halite, though the recovery of fluid inclusions by the ball-mill method is not 100%, and high concentrations of Mg2+ and Ca2+ in fluid inclusions require correction for the δD and δ18O values of the water.View full abstractDownload PDF (3817K) -
Yoshihiko Mizutani, Shinji Hayashi, Tsutomu Sugiura1986 Volume 20 Issue 6 Pages 273-285
Published: December 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSVariations in chemical and isotopic compositions of gases discharged from Kuju-Iwoyama, a fumarolic area developed in the 1738 crater of the Hosshozan volcano in Kyushu, Japan, were investigated from 1960 to 1984. The isotopic data suggest that the fumarolic condensate collected from KH-1 fumarole (the hottest fumarole of Kuju-Iwoyama) in 1960 is likely to be almost pure magmatic water, and that those collected from other low-temperature fumaroles in the early 1960s are mixtures of the magmatic water and local groundwaters. The relationship between the temperature and composition of the fumarolic gases shows that the mixing of high-temperature gases with liquid groundwater took place near the surface in the early 1960s. In 1984, the steam samples from KH-1 fumarole were found to be 1 : 1 mixtures of the steam, which had been derived from the groundwater by total evaporation, and magmatic steam, and those from other fumaroles to be mixtures of KH-1 steam and liquid groundwater. The mixing of the magmatic steam with the goundwater-derived steam suggests the penetration of groundwaters into deeper parts of the geothermal system along with the decline of fumarolic activity of the system. The isotopic and chemical geothermometer study on the gases suggests that the deep reservoir of volcanic gases was maintained at temperatures above 600°C during this investigation, and that the addition of some gaseous species (e.g., CH4, H2S and SO2) into volcanic gases took place during the passage of the gases through the geothermal system.View full abstractDownload PDF (3459K) -
Toshimori Sekine1986 Volume 20 Issue 6 Pages 287-296
Published: December 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSNear-liquidus phase relations of an andesite and the andesitic mixtures with Na2O, CaO, MgO, and iron oxide added to the andesite were determined under one-atmosphere, fO2-controlled conditions. The stability relation between clino- and orthopyroxene was determined, and pyroxenes, plagioclase and coexisting liquids (glasses) were analyzed. The liquidus temperature of plagioclase decreased and that of pyroxenes increased by the addition of Na2O, CaO and MgO, but they decreased by the addition of iron oxides. The effect of Na2O on the crystallization of minerals from andesitic melts is explained in relation to the chemical potential of wollastonite component in the liquid. The normative composition is useful to deduce the first appearance temperature of liquidus phase, and will be a satisfactory measure for the subliquidus phase if the composition of the liquidus phase is known.View full abstractDownload PDF (2903K) -
Hidehiko Shimazaki, Masaaki Shimizu, Takanori Nakano1986 Volume 20 Issue 6 Pages 297-310
Published: December 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSMany skarn deposits of various ore types occur in the Japanese island arc with genetical relation to Cretaceous and Miocene felsic igneous activities. Carbon and oxygen isotope ratios were determined for interstitial carbonates, mostly calcites, in skarn silicates from 28 representative deposits. The data obtained are compared with the isotopic composition of calcites expected to precipitate from magmatic fluids, on the assumption of isotopic equilibrium at 300–400°C between the carbonate mineral and fluid. The fluids for tungsten, tin and some copper (-iron) deposits in the regions of ilmenite-series granitic activity are characterized by 13C-depleted carbon, probably derived from organic materials in sedimentary rocks. In the fluids for most deposits of other types, such as zinc-lead, zinc-copper (-iron) and copper (-iron), magmatic carbon is predominant. Carbon and sulfur isotope values for each deposit show a positive correlation among the studied deposits, suggesting that both carbon and sulfur came from common sources. For many deposits, calculated δ18O values of the fluids are in the range from +5 to 10‰ (SMOW). Such fluids are either magmatic in origin, or are isotopically equilibrated with felsic igneous rocks. Fluids with 18O-depleted nature are recognized in some, mainly zinc-lead and zinc-copper (-iron), deposits, suggesting a contribution of surface-derived water to the formation of these deposits.View full abstractDownload PDF (3866K) -
P. K. Kuroda, S. N. Bakhtiar1986 Volume 20 Issue 6 Pages 311-316
Published: December 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe origin of the isotopically anomalous magnesium components reported to have been discovered in high-temperature mineral inclusions of carbonaceous chondrites can be attributed to the alterations of the isotopic composition caused primarily by high-energy proton reactions, which occurred within the solar system when the Sun was in its T-Tauri phase.View full abstractDownload PDF (1652K)
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