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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 2
Displaying 1-6 of 6 articles from this issue
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C. Dueñas, M. C. Fernandez, M. de la Torre1986 Volume 20 Issue 2 Pages 61-69
Published: April 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe flux of 222Rn and O2 from shallow water off the Bay of Málaga has been measured. The mean value of flux of 222Rn is evaluated to be 74 atoms/m2·s. The Bay is a weak source of oxygen to the atmosphere, where the net production of oxygen is found to be 1.82 mol/m2·y. Moreover, the gas exchange rates of 222Rn and O2 across the air-sea interface has been determined by the radon method. The gas exchange rates and the wind speed have been estimated.View full abstractDownload PDF (2422K) -
Jun-ichi Matsuda, Keisuke Nagao1986 Volume 20 Issue 2 Pages 71-80
Published: April 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe dried sediments from a single deep-sea sediment core taken in the eastern equatorial Pacific (1°02.2′N, 121°10.4′W), showed progressive enrichment in heavy noble gases (36Ar, 84Kr, 132Xe). Meanwhile, light noble gases (4He, 20Ne), especially 20Ne, were severely depleted. The noble gas abundances classified into type 1, observed in terrestrial sedimentary rocks and natural gases, can be formed as a mixture of the observed noble gas abundances with those in water. The concentrations of 84Kr and 132Xe show no systematic variation with depth, and correlated directly with the SiO2 content and inversely with the CaCO3 content. Leaching experiments to remove CaCO3 confirmed that siliceous fossils were better adsorbers of heavy noble gases than calcareous fossils. Very high 3He/4He ratios of 0.7 × 10-4 and 1.3 × 10-4 were observed in these leached samples.View full abstractDownload PDF (2588K) -
Takayoshi Kurata, Shizuo Tsunogai1986 Volume 20 Issue 2 Pages 81-90
Published: April 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSTwo kinds of soils undisturbed for the past 100 years were obtained as core samples at several sites in Japan: one that have been exposed to rainfall and the other that have not at least these 100 years. These soil samples were determined for 226Ra and 210Pb. The deficiency of 210Pb relative to 226Ra was observed in all the soil samples without rain. This is due to exhalation of 222Rn. The surpluses of 210Pb activities in the soil exposed to rain relative to those in the soil without rain at the same site were observed in the top 30cm of the core. The 222Rn exhalation rates and the supported 210Pb profiles were evaluated using a steady state vertical diffusion model of 222Rn. The 222Rn exhalation rates in the soil samples are estimated to be 0.6-2.0 atoms cm-2s-1. The 210Pb deposition rates were determined from the inventories of excess 210Pb relative to the supported 210Pb in the soil samples. These rates are 1.1-2.6dpm cm-2y-1, which are closed to the directly observed values for 2 years at nearby locations. The 210Pb deposition rates estimated regardless of 222Rn loss from the excess 210Pb relative to 226Ra are underestimated by about 10-50% for the soils studied. It is shown that the correction for the 222Rn loss is particularly important for the soils with small activity ratios of 210Pb/226Ra (<10) at the surface.View full abstractDownload PDF (2435K) -
Eizo Nakamura, Ian McDougall, Ian H. Campbell1986 Volume 20 Issue 2 Pages 91-99
Published: April 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSeven new K-Ar age determinations are presented on whole rock samples from alkaline and tholeiitic basalts of the Higashi-Matsuura district, northwestern Kyushu, Japan. Ages obtained range from 2.92 ± 0.03Ma to 3.01 ± 0.04Ma; these ages are essentially identical within analytical errors and yield an average age of 2.98 ± 0.03Ma (Late Pliocene). When combined on an isochron type diagram the six Higashi-Matsuura samples give an age of 3.00 ± 0.03 Ma with the composition of nonradiogenic 40Ar/36Ar = 294.2 ± 2.0. The excellent age agreement of samples with different K contents and petrographic characteristics provides strong evidence that the tholeiitic and alkaline basalts were erupted for an extremely short period in the Higashi-Matsuura district. A basalt from Ogawashima Island yields a K-Ar age of 3.58 ± 0.04Ma. This study and previously reported data support the hypothesis that alkaline volcanic activity in southwestern Japan commenced some 10Ma ago and continued intermittently until Recent times. Systematic variations of age and distribution of Cenozoic alkaline basalts are recognized in northeastern China, Korea and southwestern Japan. It is suggested that these variations are related to the initiation of “mantle plumes” resulting from convection in the mantle wedge caused or controlled by subduction of the Kula and Pacific plates.View full abstractDownload PDF (2767K) -
P. K. Kuroda, S. N. Bakhtiar1986 Volume 20 Issue 2 Pages 101-104
Published: April 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe origin of the isotopically anomalous oxygen components found in various meteorites can be attributed to an intense irradiation of the solar system materials during the T-Tauri phase of the young Sun. Such an irradiation is expected to have produced large isotopic anomalies for oxygen, but not for silicon, in the meteorites.View full abstractDownload PDF (973K) -
K. K. Saebo, P. K. Kuroda1986 Volume 20 Issue 2 Pages 105-110
Published: April 20, 1986
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSThe present composition of atmospheric xenon and xenon in carbonaceous chondrites and other meteorites is shown here to result from high-energy proton irradiation on a primitive composition, which gives rise to secondary neutron-capture effects. With this new theory, we calculate a primordial (p-process) composition line and a spallogenic (x-process) composition line for the light isotopes 124Xe and 126Xe. All experimental values essentially lie between these two lines on a three isotope plot. Under these circumstances, it is not necessary to invoke exotic solar system material to explain the xenon anomalies observed in the carbonaceous chondrites.View full abstractDownload PDF (1569K)
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