巻号一覧
17 巻 (1983)
- 6 号 p. 269-
- 5 号 p. 223-
- 4 号 p. 165-
- 3 号 p. 111-
- 2 号 p. 63-
- 1 号 p. 1-
17 巻, 4 号
選択された号の論文の4件中1～4を表示しています
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S. V. S. Murty, P. N. Shukla, P. S. Goel1983 年 17 巻 4 号 p. 165-183
発行日: 1983/08/20
公開日: 2008/04/08
ジャーナル フリーNitrogen contents have been determined by neutron activation method in stone meteorites and silicate standards. Leaching and sieving experiments on standards indicate that contamination from atmospheric nitrogen is negligible. For BCR-1 nitrogen contents show a range from 15 to 62ppm. The study includes 32 chondrites belonging to various classes and six achondrites. Nitrogen is high in Cl and C2 chondrites (500 to 1, 000ppm) and in E chondrites (100–500ppm). C3 group shows variable amounts of nitrogen. Ordinary chondrites have similar nitrogen contents (∼30ppm) irrespective of their petrologic group. For all classes of meteorites, chondrules have lower nitrogen compared to the matrix. Dark phases of some gas-rich meteorites are enriched in nitrogen as compared to their light counterparts. Non-magnetic portions have slightly excess N compared to the magnetic portions. Correlation of N with C, In, Bi, Tl, Zn and Cd indicates the presence of two host phases for N.抄録全体を表示PDF形式でダウンロード (4493K) -
Akira Ueda, Hitoshi Sakai1983 年 17 巻 4 号 p. 185-196
発行日: 1983/08/20
公開日: 2008/04/08
ジャーナル フリーRock and mineral powders are decomposed at 280°C in vacuum with phosphoric acid containing Sn2+ as a reducing agent (Kiba reagent). Sulfate and sulfide sulfur in the samples are extracted in liquid nitrogen-cooled traps as SO2 and H2S, respectively, while carbonate carbon is collected as CO2. The three gases are separated from each other by successive vacuum distillation. The H2S is converted to SO2 by reaction with Cu2O. The three gases, that is, two SO2 and one CO2 are measured volumetrically for the concentrations of these species and mass spectrometrically for their isotope ratios. The uncertainties in the measurements of concentration and isotope ratio of sulfur and carbon in rocks are ±5% and ±0.3‰, respectively, in most cases. The technique is suitable for the analyses of micro-amounts of sulfur and carbon in rocks. A few grams of rock sample generally suffices for the chemical and isotopic analyses of sulfur and carbon (carbonate). Some of the results so far obtained on volcanic rocks are discussed briefly in order to demonstrate the usefulness as well as the limitations of the technique.抄録全体を表示PDF形式でダウンロード (3509K) -
Hidehiko Shimazaki, Masahiro Yamamoto1983 年 17 巻 4 号 p. 197-207
発行日: 1983/08/20
公開日: 2008/04/08
ジャーナル フリーSulfur isotope ratios of sulfide minerals from the Akatani, Iide and Waga-Sennin skarn deposits formed in the “Green Tuff” region, fall in a rather broad range from +2.8 to +8.9‰. Estimated formation conditions of ores, that is, high oxygen fugacities and relatively low temperatures and pH, certify the predominance of sulfate sulfur over sulfide sulfur in the ore-forming solutions. Irreversible, fast precipitation of sulfide minerals from such sulfate-dominant solutions is thought to have resulted in insignificant isotopic fractionation between aqueous sulfate and sulfide minerals. The obtained range of isotopic values is almost identical with those for sulfide minerals from other type, vein and kuroko, deposits in the “Green Tuff” region. This regularity of sulfur isotope values for many different type deposits in the region suggests the possibility that ore sulfur was supplied from a common provenance, such as Miocene felsic igneous rocks, without any significant isotopic fractionations in the transportation and precipitation processes.抄録全体を表示PDF形式でダウンロード (3498K) -
Ruyuan Zhang, Bingguang Liu1983 年 17 巻 4 号 p. 209-221
発行日: 1983/08/20
公開日: 2008/04/08
ジャーナル フリーThis paper describes petrology and chemistry of kimberlites from four localities in North China. The distribution pattern of kimberlite intrusions is controlled not only by large-scale but also by local-scale structures. The U-Pb ages of the kimberlites in Region A range from 77 to 88m.y. and the kimberlites in Region C are emplaced between the Cretaceous and the Eocene. Based on texture and mineralogy, the kimberlites are classified mostly as basaltic kimberlite, which is composed of olivine, phlogopite, pyrope and spinel in a groundmass of serpentine and calcite. Their chemical composition and Si/Mg ratio show that most of selected samples except for Regions C and D are relatively uncontaminated kimberlite. The kimberlites contain lower Al2O3 and Na2O + K2O than those from other areas of the world. The unaltered relic olivines contain 92% forsterite component. The phlogopites have a Mg/(Mg + Fe) ratio ranging from 84 to 93%. The garnets are enriched in Mg, and their most abundant component is pyrope (62–70%). Garnets contain certain amounts of Cr2O3. The highest Cr2O3 content of garnet is ca. 8wt.%. The chromites have varied values in Cr/(Cr + Al) and high Ti contents. The available evidence both petrological and geochemical reveals that the kimberlitic magma was derived by partial melting of upper mantle garnet lherzolite under volatile-rich conditions, particularly rich in H2O and CO2.抄録全体を表示PDF形式でダウンロード (3851K)
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