巻号一覧
33 巻 (1999)
- 4 号 p. 207-
- 3 号 p. 141-
- 2 号 p. 67-
- 1 号 p. 1-
33 巻, 4 号
「揮発性元素の地球惑星科学」特集号
選択された号の論文の7件中1～7を表示しています
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「揮発性元素の地球惑星科学」特集号
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川本 竜彦, 佐野 有司1999 年 33 巻 4 号 p. i-ii
発行日: 1999/12/05
公開日: 2016/12/30
ジャーナル フリーPDF形式でダウンロード (233K)
総説
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井上 徹1999 年 33 巻 4 号 p. 207-219
発行日: 1999/12/05
公開日: 2016/12/30
ジャーナル フリーThis paper reviews the role of H2O in the Earth's interior, especially focuses on the effect on the melting relations of mantle materials comparing the results under anhydrous condition. Using the above results on melting under hydrous condition, the generation of komatiite magmas is discussed. Furthermore, the incorporation of H2O in the Earth's interior is discussed using the recent results of dehydrations of slab constituent hydrous materials.抄録全体を表示PDF形式でダウンロード (1400K)
報文
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寺田 貴洋, 河村 雄行, 秋月 瑞彦1999 年 33 巻 4 号 p. 221-233
発行日: 1999/12/05
公開日: 2016/12/30
ジャーナル フリーMolecular dynamics (MD) simulation was carried out to obtain positions and energy states of hydrogen in nominally anhydrous mantle minerals. An appropriate OH interatomic potential model (Morse-AT) was determined to reproduce vibrational spectrum and bulk modulus of brucite Mg(OH)2. Pressure gradient of OH stretching peak position in brucite is negative, showing increase of hydrogen bonding energy with pressure. This developed Morse-AT model was applied for hydrous forsterite, wadsleyite and ringwoodite Mg2SiO4. Based on the MD simulations, the small amounts of hydrogen in forsterite forms a Si-OH bond, showing lack of the hydrogen bond. In wadsleyite, the O1-site is partially replaced by OH with M3 site magnesium vacancy. In ringwoodite, hydrogen is present at a vacancy of Mg-site and coordinates SiO_4 tetrahedron oxygen. Decreasing O-O interatomic length with an increasing pressure produces a strong hydrogen bond. Hydrogen in the ringwoodite becomes more stable at higher pressure.抄録全体を表示PDF形式でダウンロード (1248K)
総説
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大谷 栄治, 朝原 友紀1999 年 33 巻 4 号 p. 235-245
発行日: 1999/12/05
公開日: 2016/12/30
ジャーナル フリーWe discuss the effects of water on important igneous processes in the Archean, i.e., the komatiite magma genesis and the formation of the cratonic peridotites based on the experimental results on the effect of water on the melting relations of model mantle peridotite at 6.5 GPa. Liquidus temperature decreases by about 100℃ and the temperature interval to produce more than 60% partial melting reduces by about 50℃ in the 1〜2 wt% water bearing system at this pressure. Garnet is the first dissolved phase and the stability field of orthopyroxene expands in the conditions of the water content of about 5 wt% at 6.5 GPa. Aluminum undepleted komatiites (AUK) can be formed by melting at 200 km depth (6.5 GPa) in a hydrous mantle at significantly lower temperatures than under the dry condition. Aluminum depleted komatiites (ADK) also can be formed by hydrous melting at higher pressure. In addition, cratonic peridotites may be formed as residues of partial melting under various water contents in the Archean mantle. The stability of the cratonic mantle, tectosphere, may be explained by dehydration hardening by removal of water due to partial melting of the wet Archean mantle.抄録全体を表示PDF形式でダウンロード (1104K) -
奥地 拓生1999 年 33 巻 4 号 p. 247-254
発行日: 1999/12/05
公開日: 2016/12/30
ジャーナル フリーThe fate of H2O accreted to the primordial Earth is discussed using the results of the hydrogen partitioning experiments between molten iron and silicate melt at high pressure. Previous works related to this problem give no weight to the partitioning of hydrogen into the core, so that the origin and abundance of H2O in the hydrosphere, crust and mantle of the present Earth should be reconsidered from the viewpoint of the evolution of the primordial Earth including core formation processes. The results indicate that there is large possibility for most of H2O accreted to the Earth to be transported into the core as molten iron hydride (FeHx), rather than to be left into the hydrosphere and mantle in every case of H2O concentration in the accreting planetesimals. In other words, the mantle must have been dried up after the core formation. These results are consistent with the observed H2O concentration in the hydrosphere, crust and upper mantle of the present Earth. The presence of hydrogen in the core may quantitatively settle the problem of density deficit of the present Earth's core.抄録全体を表示PDF形式でダウンロード (925K) -
田近 英一1999 年 33 巻 4 号 p. 255-263
発行日: 1999/12/05
公開日: 2016/12/30
ジャーナル フリーThe rate of CO2 degassing to the atmosphere-ocean system via volcanism has probably changed greatly during the history of the Earth. Change of the CO2 degassing rate results in change of the atmospheric CO2 level and so the climate, through the geochemical cycle of carbon at the surface of the Earth. If the CO2 degassing may cease or weaken suddenly, a carbon geochemical cycle model coupled with ocean chemistry and the climate model predicts that the Earth's surface environment should cool very rapidly on the order of 105 yr, and, at last, fall into the globally ice covered state. The time required for this is estimated to be on the order of 106 years throughout the Earth's history, irrespective of large change of the atmospheric CO2 level with time. However, absence of geological evidence for such an exstreme climate in the past suggests that the CO2 degassing process via volcanism should have been almost contiuous, at least, on the order of >105-106 yr, which indicates continuity of plate tectonics on the Earth.抄録全体を表示PDF形式でダウンロード (1000K) -
佐々木 晶1999 年 33 巻 4 号 p. 265-274
発行日: 1999/12/05
公開日: 2016/12/30
ジャーナル フリーNoble gas data of mantle samples have distinct two end members: PLUME-type representing the lower mantle and MORB-type representing the upper mantle. The estimated high 3He and 22Ne abundance of the PLUME source should be remnant of the dissolved solar-type atmosphere into the magma ocean. Calculations of noble gas dissolution into the magma ocean of the accreting planet suggest that the estimated 3He and 22Ne abundance can be explained if the primary atmosphere existed until M〜0.4-0.5ME. This means that the early accretion of the Earth should have proceeded in the presence of the protoplanetary gas disk. The lower 4He/3He and 21Ne/22Ne of the PLUME data than MORB data can be explained if the lower mantle was less degassed during magma ocean cooling. The upper limit of the initial carbon abundance in mantle can be also estimated using C/3He data. The upper mantle should contain 3.8×1021 mole which is lower than the present crustal amount, whereas the lower mantle would contain 70 times as much carbon as the upper mantle.抄録全体を表示PDF形式でダウンロード (990K)
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