巻号一覧
20 巻 (1986)
- 6 号 p. 261-
- 5 号 p. 213-
- 4 号 p. 159-
- 3 号 p. 111-
- 2 号 p. 61-
- 1 号 p. 1-
20 巻, 5 号
選択された号の論文の7件中1～7を表示しています
- |<
- <
- 1
- >
- >|
-
P. K. Kuroda, Z. Z. Sheng1986 年 20 巻 5 号 p. 213-226
発行日: 1986/10/20
公開日: 2008/04/08
ジャーナル フリーAnomalies observed by Nagao et al. (1984) in the xenon fractions released from the carbonaceous chondrite Belgica can be explained as due to the alterations of the isotopic composition caused by a combined effect of (a) mass-fractionation, (b) high-energy proton spallation and (c) secondary neutron-capture processes, which occurred within the solar system when the Sun was in its T-Tauri phase. The isotopic composition of the xenon fraction released from this meteorite at 1, 800°C seems to represent that of the xenon which is more primordial than the atmospheric xenon.抄録全体を表示PDF形式でダウンロード (3319K) -
Yuji Sano1986 年 20 巻 5 号 p. 227-232
発行日: 1986/10/20
公開日: 2008/04/08
ジャーナル フリーTaking into account the 3He/4He ratio in pore water of Pacific deep sea sediments and the ratio variation with thickness of sedimentary layers in the continental crust area, we estimated 3He and 4He fluxes for each part of the solid earth: ocean floor, the continent, and volcanic areas. Results suggest that the 4He flux from the continent accounts for large amount of total outflow, whereas the principal sources of 3He are volcanic areas including mid-ocean ridges, hot spots and subduction zones. Helium-3 flux from the ocean floor contributes little to its mass balance in the atmosphere in spite of the ocean's dominance in the surface of the earth. Based on the total fluxes and inventories of 3He and 4He in the atmosphere, their average residence times can be obtained as 3.3 × 106 and 8.4 × 106 years, respectively.抄録全体を表示PDF形式でダウンロード (1726K) -
Akimasa Masuda, Takafumi Hirata, Hiroshi Shimizu1986 年 20 巻 5 号 p. 233-239
発行日: 1986/10/20
公開日: 2008/04/08
ジャーナル フリーOsmium isotopes in three Os reagents, four terrestiral Os-Ir alloys (iridosmine) and two iron meteorites have been measured on an inductively coupled plasma mass spectrometer (ICP-MS), with the precision of around 1% for 187Os/192Os. Comparisons are made of our isotopic ratios with the previous ones. Apart from the variation of 187Os abundance as naturally expected, there seems to be a slight systematic deviation for 189Os. Also some discussions are given to 184Os. The Os isotopic ratios for three iridosmine samples from Hokkaido, Japan, have been found quite similar to each other. The values for the Hokkaido iridosmines are 3–4% higher relative to the straight 187Os growth line obtained by Allegre and Luck (1980). Finally, the isotopic “standard” abundances (%) for Os are presented by us: 184Os, 0.019; 186Os, 1.589; 187Os, 1.519; 188Os, 13.24; 189Os, 16.37; 190Os, 26.30; 192Os, 40.96. These give us the Os atomic weight = 190.24.抄録全体を表示PDF形式でダウンロード (1713K) -
P. K. Kuroda, Z. Z. Sheng1986 年 20 巻 5 号 p. 241-248
発行日: 1986/10/20
公開日: 2008/04/08
ジャーナル フリーXenon in the solar system can be divided into two groups: (a) primordial xenon, whose isotopic composition can be approximated by that of the atmospheric xenon and (b) xenon, whose isotopic composition was severely altered by high energy proton and neutron reactions which took place during the T-Tauri phase of our Sun. The isotopic compositions of the SUCOR (surface correlated) xenon found in lunar fines and the CCFX xenon, corrected for mass fractionation and spallation effects, belong to the group (a) and the AVCC xenon and the so-called s-type xenon found in the Murchison meteorite belong to the group (b). Some of the xenon fractions recently isolated from the Allende and Belgica meteorites appear to be more ‘primordial’ than the atmospheric xenon.抄録全体を表示PDF形式でダウンロード (1975K) -
I. J. Graham, B. W. Robinson1986 年 20 巻 5 号 p. 249-253
発行日: 1986/10/20
公開日: 2008/04/08
ジャーナル フリーA 5 cm diameter nodule recently recovered from the northern slopes of Mount Ruapehu, Taupo Volcanic Zone, New Zealand consists of bladed natroalunite, quartz and rutile. The natroalunite crystals are zoned, having K-rich cores and Na-rich rims, and are enriched in Ba and Sr over Rb. The strontium isotopic composition (0.70535) is close to the average for Ruapehu lavas and the δ34S (‰) CDT value of +16.1 is similar to dissolved sulphate in Ruapehu crater lake. The nodule probably originated as a precipitate from hydrothermal fluids at low pH, and was subsequently baked by hot lava.抄録全体を表示PDF形式でダウンロード (1394K) -
Hiroshi Nagasawa, Kanenori Suwa1986 年 20 巻 5 号 p. 253-260
発行日: 1986/10/20
公開日: 2008/04/08
ジャーナル フリー3.5-billion-year-old cherts from Onverwacht Group, Swaziland System in the Barberton area, South Africa were analyzed for rare earth elements (REE), Sc, Hf, Fe, Cr, Co and Na by means of instrumental neutron activation analysis (INAA). The Onverwacht cherts showed less fractionated REE abundances compared with those in younger cherts and other sedimentary rocks. The chondrite-normalized La/Yb ratios observed for the samples from the older Theespruit Formation and younger Hooggenoeg Formation of the Onverwacht Group are 1.2∼2.5, and 4.6, respectively. These values are smaller than the La/Yb values observed for the Fig Tree Group (5.5) and Moodies Group (7.8), which overlie the Onverwacht Group in the Barberton area, indicating an increasing trend for La/Yb ratio in the sedimentary rocks with time in the Swaziland System. The results appear to indicate that the relative fractionation between light and heavy REE in the crustal region which had supplied REE to the sedimentary rocks increased with time in the Archaean era from nearly chondritic La/Yb ratio to about the present-day value in a very short time span of a few hundred million years. Absence of Ce anomaly, together with variable Eu anomalies in the REE patterns, possibly shows reducing conditions in the sedimentary environments. It is also suggested that the negative Eu anomalies commonly observed for the post Archaean sedimentary rocks were derived by accumulation of plagioclase in the lower continental crust by sinking of plagioclase in magmas in the upper crust.抄録全体を表示PDF形式でダウンロード (1786K) -
Hiroshi Nagasawa, Kanenori Suwa1986 年 20 巻 5 号 p. 255-260
発行日: 1986/10/20
公開日: 2008/04/08
ジャーナル フリー3.5-billion-year-old cherts from Onverwacht Group, Swaziland System in the Barberton area, South Africa were analyzed for rare earth elements (REE), Sc, Hf, Fe, Cr, Co and Na by means of instrumental neutron activation analysis (INAA). The Onverwacht cherts showed less fractionated REE abundances compared with those in younger cherts and other sedimentary rocks. The chondrite-normalized La/Yb ratios observed for the samples from the older Theespruit Formation and younger Hooggenoeg Formation of the Onverwacht Group are 1.2∼2.5, and 4.6, respectively. These values are smaller than the La/Yb values observed for the Fig Tree Group (5.5) and Moodies Group (7.8), which overlie the Onverwacht Group in the Barberton area, indicating an increasing trend for La/Yb ratio in the sedimentary rocks with time in the Swaziland System. The results appear to indicate that the relative fractionation between light and heavy REE in the crustal region which had supplied REE to the sedimentary rocks increased with time in the Archaean era from nearly chondritic La/Yb ratio to about the present-day value in a very short time span of a few hundred million years. Absence of Ce anomaly, together with variable Eu anomalies in the REE patterns, possibly shows reducing conditions in the sedimentary environments. It is also suggested that the negative Eu anomalies commonly observed for the post Archaean sedimentary rocks were derived by accumulation of plagioclase in the lower continental crust by sinking of plagioclase in magmas in the upper crust.抄録全体を表示PDF形式でダウンロード (1786K)
- |<
- <
- 1
- >
- >|