| Project/Area Number |
07454138
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
地球化学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
HIYAGON Hajime Univ.of Tokyo, Graduate School of Science, Research Associate, 大学院・理学系研究科, 助手 (70192292)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥4,200,000 (Direct Cost: ¥4,200,000)
Fiscal Year 1996: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1995: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Keywords | nitrogen / noble gas / solubility / solid-melt partition / silicate melt / oxygen fugacity / atmosphere / mantle / 大気形成 / 固液分配係数 / 酸素分圧依存性 / ヘンリーの定数 / 同位体非平衡 |
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| Research Abstract |
In order to understand the evolition of the Earth's atmosphere-mantle system based on nitrogen, I conducted experiments on pertitioning of nitrogen and noble gases between (A) gas-silicate melt and (B) soild (cpx)-silicate melt. Experiment (A) was conducted under various conditions : T=1300-1600ﾟC,P(N_2)=0.5-1000 atm f(O_2)=IW-2 to IW+10 (logarithmic scale). The results show that (1) concentration of dissolved nitrogen is linearly correlated with P(N_2)(i.e., Henry's Law is obeyed), (2)nitrogen solubility (Henry's constant) has very weak dependence on temperature (3) and on f(O_2), and is approximately equal to that of Ar. All these observations suggest physical dissolution of nitrogen (i.e., dissolution as nitrogen molecules) in basaltic melt in the present experimental conditions. This is also suppoeted by the observation that almost no isotopic exchange occured between ^<15>N^<15>N-enriched nitrogen and normal nitrogen (^<14>N^<14>N-dominated) during dissolution nd extraction of nitrogen in and from the basaltic melt (glass) synthesized under a highly oxydizing condition. In experiment (B), a clinopyroxene (cpx)-basaltic melt pair wes synthesized using a piston-cylinder-type apparatus at 15kbar and 1350-1270ﾟC.The obtainned cpx/melt partition coefficients are 0.06 for nitrogen and 0.11 for argon, not significantly different with each other. The results of the two experiments imply that magmatic processes may not produce large fractionation between nitrogen and argon. Therefore, the two orders of magnitude difference in the N/^<36> Ar ratios of the atmosphere (-10^4) and the mantle (-10^6) must be the result of some processes other than the magmatic ones.
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