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Volume 29 (1995)
- Issue 6 Pages 337-
- Issue 5 Pages 277-
- Issue 4 Pages 213-
- Issue 3 Pages 163-
- Issue 2 Pages 97-
- Issue 1 Pages 1-
Volume 29, Issue 2
Displaying 1-7 of 7 articles from this issue
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Hayao Sakamoto, Takashi Tomiyasu, Norinobu Yonehara1995 Volume 29 Issue 2 Pages 97-105
Published: April 20, 1995
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSediments collected from Kagoshima Bay, Minamata Bay and Yatsushiro Sea were analyzed for organic mercury, mercury(II) oxide, mercury(II) sulfide and residual mercury through sequential extraction followed by cold vapor atomic absorption spectrometry. Results show that mercury(II) sulfide (38.4∼96.1%, geometric mean 71.4%) is the most prevalent mercury compound in the sediments followed by mercury(II) oxide (<0.9∼42.9%, geometric mean 5.65%). Organic mercury is present only in a very small quantity (0.21∼12.8%, geometric mean 2.55%). Residual mercury shows a wide range of content in the sediments (2.6∼44.3%, geometric mean 10.5%). The abnormally high mercury concentration observed in the sediment samples from Northern Kagoshima Bay is caused by the condensation of submarine fumarolic gases including elemental mercury and hydrogen sulfide, which are depositing in the surface sediments. This is in accord with the fact that mercury(II) sulfide is the most prevalent mercury compound there. Organic mercury content is high in the vicinity of the submarine fumarole, where mercury(II) sulfide content is very high.View full abstractDownload PDF (2033K) -
Yuko Soma, Atsushi Tanaka, Mitsuyuki Soma1995 Volume 29 Issue 2 Pages 107-113
Published: April 20, 1995
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSPhytoplankton pigments in the sediment of Lake Kasumigaura were analyzed by HPLC. The depth profiles of echinenone and myxoxanthophyll, which are characteristic carotenoids of blue-green algae, showed an increase after the lock gate (Hitachigawa-suimon) was constructed 30 years ago to prevent seawater coming into the lake. The depth profile of β-carotene suggests that the algal biomass in the lake decreased 30 years ago, being consistent with the period of the construction of the lock gate, and then increased with the increase of freshwater phytoplankton such as blue-green algae.View full abstractDownload PDF (1625K) -
Tasuku Akagi, Ian A. Franchi, Colin T. Pillinger1995 Volume 29 Issue 2 Pages 115-122
Published: April 20, 1995
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSOxygen from a range of minerals has been liberated by fluorination under the radiation from a Nd/YAG laser, and the isotope ratio of oxygen measured with a conventional ratio mass-spectrometer. During the fluorination, generation of fluorine gas often takes place through the dissociation of chlorine trifluoride (CIF3) and interferes with the measurement of the isotope ratio later on. Using mercury on gold to remove the F2 also led to a loss of oxygen. A simple trap made of stainless steel wool has proved to be very effective at removing of fluorine without any measurable loss of O2. The minerals analysed include quartz, feldspar, hornblende, mica, garnet, pyroxene, olivine, and spinet. The accuracy and precision of the method was evaluated. There is good agreement with data obtained by conventional fluorination for the analyses of hornblende, garnet and spinel. In the case of quartz, feldspar and pyroxene, the laser method gave isotope ratios (18O/16O) lighter than the ratios obtained by the conventional method by less than 1‰, but its application to olivine and mica gave lighter isotope ratios by as much as 1∼2‰. The precision of this method is better than 0.3‰ for all the minerals investigated.View full abstractDownload PDF (1768K) -
Hiroo Kagami, Masaki Yuhara, Yoshiaki Tainosho, Shigeru Iizumi, Masaak ...1995 Volume 29 Issue 2 Pages 123-135
Published: April 20, 1995
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSm-Nd whole rock isochron ages have been determined for metadiabase and gabbro of the Ikoma Mass in the Kinki Ryoke Belt of the Southwest Japan Arc. The ages and initial 143Nd/144Nd ratios are as follows: hornblende gabbro-norite, 180±23 Ma, 0.512180±0.000024; metadiabase, 197±31 Ma, 0.512166±0.000035; anorthositic gabbro, 169±29 Ma, 0.512148±0.000027. The combined age, using hornblende gabbro-norite and metadiabase, is 192±19 Ma (0.512169±0.000021). Similar rock types collected from other masses plot around the isochrons defined by their counterparts from the Ikoma Mass. These age data indicate that the mafic igneous activity took place in the Ryoke Belt (a late Cretaceous granitic terrane) during the middle to early Jurassic. Sm-Nd and Rb-Sr whole rock and mineral isochron ages of hornblende gabbro are 97.7±5.5 Ma and 71.8±9.5 Ma, respectively, which indicate thermal resetting of the gabbro by intrusion of granitic plutons. Cortlanditic gabbros from the Ikoma Mass and other masses do not plot on the Sm-Nd whole rock isochrons for hornblende gabbro-norite, metadiabase and anorthositic gabbro. This suggests that cortlanditic gabbros evolved independently from other gabbros. Some Ryoke gabbroic masses, including the Ikoma Mass, consist of a complex array of cumulate which crystallized from several different mafic magmas, representing different ages and sources. Gabbroic rocks which formed in the lower crust have the same Sr and Nd isotopic character as the Ryoke gabbros.View full abstractDownload PDF (3182K) -
Noriyuki Suzukii, R. Paul Philp1995 Volume 29 Issue 2 Pages 137-148
Published: April 20, 1995
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSIn order to investigate the formation of organosulphur compounds during the very early stage of diagenesis, experiments were designed to simulate sulphur incorporation from H2S, or elemental sulphur, into recently deposited natural sedimentary organic matter (cyanobacterial mats from salt ponds in Baja California) and performed under relatively mild reaction conditions (40°C, 2 to 30 days, hydrous and anhydrous). The sulphur-containing moieties in the reaction products were examined by pyrolysis-gas chromatography (GC) using a GC equipped with a flame photometric detector (FPD) and a flame ionization detector (FID), and pyrolysis-gas chromatography/mass spectrometry (GC/MS). Sulphur incorporation from H2S into recently deposited cyanobacterial mats occurred fairly readily, but elemental sulphur does not react as readily with the cyanobacterial mats. Sulphur incorporation into humic acids occurred more rapidly than into proto-kerogens. Sulphur incorporation into lipid fractions was not observed. Two major sulphur incorporation stages are proposed, with the formation of thiols by reaction between H2S and active carbonyl groups considered to be the most likely mechanism of sulphur incorporation in the first stage. The second stage of sulphur incorporation is proposed to be related to the reaction between H2S and proteinaceous organic matter.View full abstractDownload PDF (3106K) -
Hiroyuki Kitagawa, Eiji Matsumoto1995 Volume 29 Issue 2 Pages 149-153
Published: April 20, 1995
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThree-dimensional maps of stable carbon isotope ratio (δ13C) are presented for wood trunks of Japanese cedars (Cryptomeria japonica) from Yakushima Island, southern Japan. The variations in δ13C within the wood trunks of both young cedars and a giant Japanese cedar with 1846 annual rings are very small (±0.1‰ on average), suggesting that fossil wood and small wood fragments collected from archeological sites and drill-cores of sediments could be applied to the studies of paleo-environment.View full abstractDownload PDF (1231K) -
Hiroshi Nagasawa, Hisayoshi Yurimoto, Masana Morioka1995 Volume 29 Issue 2 Pages 155-161
Published: April 20, 1995
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSHf-Zr interdiffusivity in zircon has been determined on hafnon-zircon double-layered crystals using back-scattered electron image contrast in a scanning electron microscope. The observed Hf-Zr interdiffusion coefficient at 1600°C and 1500°C in the direction perpendicular to the c-axis is 2×10-15 and 3×10-16 cm2/sec, respectively. The value observed at 1600°C perpendicular to the c-axis is about an order of magnitude higher compared with the value of ∼2×10-16 cm2/sec along the c-axis. These observed low diffusivity values suggest that diffusivities of Th and U in zircon are expected to be similarly low.View full abstractDownload PDF (1735K)
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