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Volume 35, Issue 1
Displaying 1-7 of 7 articles from this issue
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Chan-Ho Jeong2001 Volume 35 Issue 1 Pages 1-12
Published: February 20, 2001
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe abandoned Samkwang mine area was chosen as the research site for radioactive waste disposal in Korea. The study site chiefly consists of Pre-cambrian granitic gneiss, which is considered as potential host rock of a radioactive waste repository. In this study, the chemical composition and residence time of groundwater collected at different depths and locations in the mine adits and boreholes nearby the mine were investigated. The factor analysis of hydrochemical data was applied to illustrate mineral-water reaction processes controlling the chemical composition of groundwater. Three chemical types of groundwater were recognized: Ca-HCO3 type of shallow groundwater and Ca(Mg)-SO4(HCO3) type of shallow and deep groundwater in the mine, and Na-HCO3 type of borehole groundwater. Tritium level indicates that the deep and borehole groundwater is older water recharged before 1950's, and that shallow groundwater is younger water recharged after 1950's. Thermodynamic equilibrium states between major minerals and water samples were calculated in the term of the activities of chemical constituents. The results of this study show that groundwater chemistry in the study area was evolved through the dissolution of calcite, chlorite, albite and sulfides, and the precipitation of clay and oxide minerals. The results of this study would be useful for the assessment of hydrochemical and mineralogical effects on the fate of radionuclides along groundwater pathways in the abandoned mine as a potential radioactive waste repository.View full abstractDownload PDF (349K) -
George W. A. Nyakairu, Christian Koeberl2001 Volume 35 Issue 1 Pages 13-28
Published: February 20, 2001
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSClay-rich sediments from the Kajjansi, Kitiko, Kitetika, and Ntawo valleys in central Uganda were analyzed for mineralogical and chemical composition, including the rare earth element (REE) contents. The valleys are filled with Quaternary to Recent alluvial and lacustrine sands, silt, and gravels, which formed from the bed rock metasediments of the Buganda-Toro System and from granitoid rocks that include rocks of the basement. The sediments are dominated by kaolinite and quartz, and minor phases include smectite, chlorite, and illite/muscovite. Whole rock chemistry shows that sediment samples rich in SiO2 have low Al, Fe, Sc and Cr contents. The high chemical index of alteration (CIA) values (87 to 96), chemical index of weathering (CIW) values around 98 and low contents of the alkali and alkali earth elements of the clay-rich sediments suggest a relatively more intense weathering source area. Barium, Rb, Ca, and Mg were probably flushed out by water during sedimentation. The chondrite-normalized REE patterns of the clay-rich sediments show LREE enrichments and a negative Eu anomaly. The high chondritenormalized La/Yb ratios, and Gd/Yb ratios lower than 2.0, indicate that the sediments are enriched in the LREEs and are similar to typical post-Archean shales, such as Post-Archean Australian Shale (PAAS). The mineralogical composition, REE contents, and elemental ratios in these sediments suggest a provenance from mainly felsic rocks, with only minor contributions from basic sources. The basic sediments were most likely derived from metasedimentary rocks, such as muscovite-biotite schists, which are characteristic of the Buganda-Toro System rocks, whereas the felsic sediments are derivatives of granitoid rocks of the basement. The most significant geochemical finding is that despite intense weathering, which has affected most elements, the REE, Th, and Sc remain immobile.View full abstractDownload PDF (855K) -
Katsuhiko Suzuki, Martin Feely, Cian O'Reilly2001 Volume 35 Issue 1 Pages 29-35
Published: February 20, 2001
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSRe-Os ages were determined for molybdenites from the late-Caledonian Galway Granite in the west of Ireland. Molybdenites from three localities within the batholith, Mace Head, Murvey, and Travore, yield respective Re-Os ages of 425.2 ± 3.1 Ma, 383.2 ± 8.1 and 426.1 ± 5.5 Ma, and 338.9 ± 5.6 and 464 ± 28 Ma. The molybdenites from the three localities are believed to be contemporaneous. However, the Re-Os ages obtained for each locality are not only in disagreement with the ages of the samples from the other localities but also are inconsistent within a single locality. Replicate analyses of a molybdenite standard (HLP-5) characterized by AIRIE using our method (Suzuki et al., 1992) yields reproducible Re-Os ages, which are in agreement with the results of Markey et al. (1998). Therefore, the age discrepancies in Galway molybdenites in this study should not be attributed to analytical errors. Suzuki et al. (2000) revealed experimentally that the Re-Os system in molybdenite can behave as an open-system when immersed in warm aqueous NaCl or NaHCO3 bearing fluid. Detailed fluid inclusion studies of molybdenite vein quartz and granite quartz (Gallagher et al., 1992; O'Reilly et al., 1997) have shown that the Galway Granite was the locus for repeated fluid events, i.e., 1. Expulsion of aqueous carbonic magmatic fluids during the final stages of crystallization, 2. Meteoric fluid convection probably driven by waning magmatic heat and 3. Incursion of basinal brines associated with fluorite mineralization at least 100 Ma after granite consolidation. We suggest that younger hydrothermal fluids perhaps associated with fluorite mineralization may have perturbed the Re-Os systematics of molybdenites from the Galway Granite.View full abstractDownload PDF (153K) -
Hideyuki Katsumata, Akira Shimoyama2001 Volume 35 Issue 1 Pages 37-48
Published: February 20, 2001
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSAlkyl and polynuclear aromatic thiophenes were detected in sedimentary rocks of a stratigraphic sequence from Miocene to Pliocene in Shinjo basin, Japan. C25 Highly branched isoprenoid (HBI) thiophenes, dibenzothiophene, C1- and C2-alkyldibenzothiophenes, and benzo[b]naphto[1, 2-d]thiophene were rather predominantly present. The C25 HBI thiophenes consist of three isomers including a pair of diastereomers. They were present in sediments from the Nakawatari to the upper part of the Kusanagi Formations and absent at the middle and lower parts of the Formation. The depth profiles of their concentrations do not coincide with those of the C25 HBI alkane concentration and bulk sulfur content in the same sediment samples. It is postulated that the C25 HBI thiophenes and the C25 HBI alkane were produced by the reaction of C25 HBI alkadiene and C25 HBI polyene, respectively, with reduced sulfur during early diagenesis. The variation in composition of the C25 HBI thiophene isomers was observed in the sediments, suggesting that they were derived from different kinds of C25 HBI alkadienes. The concentrations of the polynuclear aromatic thiophenes showed an increasing trend downwards the upper to middle Kusanagi Formation. Among these thiophenes dibenzothiophene and benzo[b]naphto[1, 2-d]thiophene concentrations varied from 10 to 730 and 14 to 210 pmol g-1, respectively. The depth profiles of their concentrations were different from that of the C25 HBI thiophenes. It is likely that the polynuclear aromatic thiophene formation started from different precursors followed by different processes from those of the C25 HBI thiophenes.View full abstractDownload PDF (387K) -
Mitsuo Uematsu, Kazutake Ohta, Kiyoshi Matsumoto, Itsushi Uno2001 Volume 35 Issue 1 Pages 49-57
Published: February 20, 2001
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSTo determine the variability of chemical properties in marine aerosols, a stationary shipboard measurement study was carried out at a station over the Northwest Pacific for 29 hours in the summer of 1999. Under a North Pacific high pressure system, carbonaceous substances, major inorganic ions, and particle numbers of typical marine aerosols were measured with little influence from continental and anthropogenic sources. The mass median diameter of organic aerosol was larger than 0.5 μm and its behavior over time was similar to sea-salt aerosol. Although the source of marine organic aerosol was believed to be mainly from continents, this result suggested that organic substances in micro layer of the sea surface is one of the sources to supply fine organic aerosol to the marine atmosphere. The further investigation would be necessary over various oceanic regions to find out the effects of marine biological activities.View full abstractDownload PDF (643K) -
Tatsuo Maekawa2001 Volume 35 Issue 1 Pages 59-66
Published: February 20, 2001
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe equilibrium conditions were experimentally determined for gas hydrate of methane and ethane mixtures in pure water and 3.0 wt% NaCl solution. The present results indicate that the addition of ethane stabilizes gas hydrate and shifts the equilibrium conditions to higher temperature and lower pressure. As ethane concentration increases from 0 vol% to 10 vol%, the equilibrium pressure of gas hydrate decreases non-proportionally with gas composition, which implies a change in the hydrate structure over this range of gas composition. The equilibrium temperature of gas hydrates of methane and ethane mixtures in 3.0 wt% NaCl solution is approximately 1.0 K lower than that in pure water at a constant pressure.View full abstractDownload PDF (452K) -
Hideyuki Katsumata, Akira Shimoyama2001 Volume 35 Issue 1 Pages 67-76
Published: February 20, 2001
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSOne C25 highly branched isoprenoid (HBI) thiophene, one C25 HBI alkane, and five polynuclear aromatic thiophenes were detected in the Cretaceous/Tertiary (K/T) boundary sediments at Kawaruppu, Hokkaido, Japan. The C25 HBI thiophene was found only in the sediments below the boundary claystone but not in the claystone and sediments above it. On the other hand, the C25 HBI alkane was present in all the sediments. However, its concentration was low below and over the lower two thirds of the claystone, but increased in the upper one third. This distribution pattern resembles that of the longer chain n-alkanes (Mita and Shimoyama, 1999a). The depth profiles of the thiophene and alkane concentrations possibly reflect the massive extinction of organisms. Among the polynuclear aromatic thiophenes, dibenzothiophene and benzo[b]naphto[1, 2-d]thiophene are relatively abundant. Their concentrations were roughly constant in the sediments below the horizon at the upper one third of the boundary claystone. Their concentrations began to increase at the one third horizon towards the 40 cm horizon (26 cm above the top horizon of the claystone) and then steeply decreased in the sediment above the horizon. A nearly constant ratio of 4- to 1-methyldibenzothiophene found in the sediments above, within, and below the boundary claystone indicates that diagenesis has occurred evenly over the sediments. The depth profile of the dibenzothiophene concentrations resembles that of the reported sulfide contents (Kajiwara and Kaiho, 1992) suggesting that polynuclear aromatic thiophene formation is related in some way to sulfide content at deposition.View full abstractDownload PDF (232K)
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