巻号一覧
30 巻, 1 号
選択された号の論文の5件中1～5を表示しています
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Hidekazu Matsueda, Hisayuki Y. Inoue, Masao Ishii, Yoshifumi Nogi1996 年 30 巻 1 号 p. 1-15
発行日: 1996/02/20
公開日: 2008/04/08
ジャーナル フリーAtmospheric methane mixing ratios were measured over the North Pacific during the winter season from 1987 to 1993 to extend our methane record since 1978. The latitudinal distribution of methane mixing ratio showed a north-to-south gradient from mid-latitudes to the equator every year. A sharp mixing ratio gradient often appeared at the boundary between the winter monsoon and the trade wind regions around 20°N. No significant longitudinal gradient was found during the winter season, although methane levels along the equator showed a large difference between the western and eastern Pacific. The overall methane increase rate in the western Pacific was estimated to be 13 ppb/yr on the basis of the long-term record for 15 years from 1978 to 1993. This record indicates that the methane growth rate over this Pacific region was gradually slowing down until 1990, followed by no significant increase in the 1990's. The overall deceleration of the growth rate was more rapid in the middle latitudinal zone (20°N–30°N) than in the lower latitudinal zone (3°N–20°N). This latitudinal difference suggests a rapid reduction of methane emissions from the continental regions. The methane growth rate showed an interannual variation with an increasing trend around 1983 and 1987, which was roughly related to the El Niño events. It is suggested that the methane growth rate was affected by a change of interhemispheric transport due to the ENSO events.抄録全体を表示PDF形式でダウンロード (4265K) -
Jauh-tzuoh Lee, Bin Li, O. K. Manuel1996 年 30 巻 1 号 p. 17-30
発行日: 1996/02/20
公開日: 2008/04/08
ジャーナル フリーTwo FeS-rich samples from the Allende (C3V) chondrite were analyzed for Xe and Kr. One sample was irradiated in a neutron flux to generate a tracer isotope of Xe by the 130Te(n, γ2β–)131*Xe reaction. The experiment was designed to use this tracer isotope to identify the temperature at which gases were released from within the sulfide. When the sulfide melted at 950°C, the Xe released was terrestrial in isotopic composition, except for enrichments from spallogenic and radiogenic components. It is concluded that terrestrial-type Xe, Xe-T, was a primordial component that was dominant in the inner Fe, S-rich region of the solar nebula.抄録全体を表示PDF形式でダウンロード (3682K) -
Tetsumaru Itaya, Masako Doi, Takeshi Ohira1996 年 30 巻 1 号 p. 31-39
発行日: 1996/02/20
公開日: 2008/04/08
ジャーナル フリーIn order to meet the challenge of the K-Ar age determination of mafic and ultramafic rocks from ophiolite complexes in orogenic belts. we developed a convenient and precise method of analyzing low and very low potassium in rock and mineral using ordinary flame photometry. The method which uses a newly designed and constructed ultra low blank chemical line makes it possible to analyze potassium as low as 0.001 wt.% in a rock or mineral by flame photometry with about 1% blank contribution to the sample potassium. The method was applied to igneous and metamorphic hornblendes from the Mikabu and Poroshiri ophiolite complexes, and to coexisting hornblende and clinopyroxene from the Cretaceous volcanic rocks in the Tanba and Nohi areas. The results revealed that the conventional K-Ar ages obtained are consistent with the geology of the host rocks. Hornblende (0.487 wt.% of K) and clinopyroxene (0.0563 wt.% of K) from a basaltic andesite in the Tanba area have the same age (ca. 100 Ma), and clinopyroxene (0.0119 wt.% of K) from the Nohi basaltic andesite gives the age of 59 Ma which is completely consistent with the recent chronological data. This strongly suggests that the clinopyroxene in the Cretaceous volcanic rocks had no significant amount of exess argon in primary isotopic systematics.抄録全体を表示PDF形式でダウンロード (2368K) -
Masayuki Minakawa, Shinichiro Noriki, Shizuo Tsunogai1996 年 30 巻 1 号 p. 41-55
発行日: 1996/02/20
公開日: 2008/04/08
ジャーナル フリーTotal dissolvable manganese (TDMn) was measured at 13 stations in the East China Sea and the Yellow Sea. High manganese concentrations of more than 100 nmol/1 were observed at stations near the Yangtze River estuary and in the bottom water of the central Yellow Sea, while the manganese concentration dramatically decreased toward the shelf break and reached a constant value less than 5 nmol/l in the Kuroshio water. The manganese concentration increased toward the bottom at almost stations. These data confirm that manganese is released from the seafloor of the continental shelf. Applying a box model to the continental shelf water shallower than 150 m deep, the residence time and the benthic flux of manganese have been calculated to be (140 ± 62) days, (11 ± 4) × 103 nmol/m2/day from the whole bottom area of 0.9 × 1012 m2, respectively. The fraction of manganese transported into the East China Sea across the 700 km-long border from outside the sea via the near bottom layer is estimated at 55% of total input to the region. The flux of terrigenous particles exported to the pelagic ocean amounts to 8% of the total suspended load discharged from the Yangtze and Yellow rivers.抄録全体を表示PDF形式でダウンロード (3325K) -
Hiroshi Shimizu, Seung-Gu Lee, Akimasa Masuda, Mamoru Adachi1996 年 30 巻 1 号 p. 57-69
発行日: 1996/02/20
公開日: 2008/04/08
ジャーナル フリーNeodymium and cerium isotopic ratios, rare earth clement abundances and major element compositions were determined for Precambrian orthogneiss and granite clasts in the Jurassic Kamiaso conglomerate from central Japan. Three types of REE patterns are observed for the Kamiaso samples: (1) reverse S-shaped patterns with high enrichment of LREE, (2) patterns consisting of upward convex La-Nd span and reverse S-shaped Nd-Lu span, and (3) patterns consisting of two or three rectilinear lines with an inflection at Ho (and Nd). Sm-Nd data on these rocks give an age of 2.07 ± 0.06 Ga (2σ) with εNd (2.07 Ga) = –1.9 ± 0.4. The Sm-Nd age is in accordance with the Rb-Sr whole-rock age of 2.05 Ga for quartzo-feldsparthic gneiss clasts by Shibata and Adachi (1974), confirming that the age of ca. 2.05 Ga indicates the time of formation of the original granitic rocks. The initial value of εNd (2.07 Ga) = –1.9 shows slightly enriched or chondritic feature for the source of original granitic rocks at 2.07 Ga. This study shows that Precambrian episodes and protolithic features can be understood from Precambrian orthogneiss and granite clasts in Mesozoic conglomerates, since the clasts have not undergone post-depositional thermo-tectonic influences.抄録全体を表示PDF形式でダウンロード (3124K)
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