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High-pressure on the structure and dynamics of the deep earth's interior.

高压对地球深层内部结构和动力学的影响。

基本信息

批准号：
01460052
负责人：
ITO Eiji
金额：
$ 3.97万
依托单位：
Okayama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1991
项目状态：
已结题

项目摘要

The detailed phase diagrams of the olivine-modified spinel-spinel and the post spinel transformations, were constructed for the system Mg_2SiO_4-Fe_2SiO_4. The mantle spinel dissociates into perovskite (Pv) and magnesiowustite (Mw) within a depth interval less than 4 km making the 650 km discontinuity be sharp. This feature provide a fixed point of mantle temperature at 650 km depth and a standard temperature profile of the upper mantle was proposed. The dynamic nature of descending slabs was analyzed. The characteristics of deep focused earthquakes are well explained in terms of plunging and buoyant forces acting on the slabs caused by the distortions of phase boundaries. It was also pointed out that the sudden disappearance of seismic activity around 700 km depth would be due to the superplasticity associated with the breakdown assemblage of Pv and Mw.Results of subsolidus and melting experiments on MgCO_3 and the system MgCO_3-MgSiO_3 conducted up to 25 GPa and 2000 ﾟC revealed that … More , in the depths greater than 140 km, CO_2 no longer behaves as a volatile component but is fixed as magnesite, and that CO_2 is progressively released into the atmosphere by the igneous process. Examination of the solubility of CO_2 into H_2O fluid at high P and T made it possible to discuss the recycling process of CO_2 by taking the subduction into consideration.Extensive effort was focused on the melting relations of the lower mantle materials. MgSiO_3 Pv melts congruently at about 2500 ﾟC and 23 GPa with a dTm/dP slope of about 25ﾟ/GPa. The melting reration of the MgO-FeO-SiO_2 system exhibits a eutectic melting between Pv and Mw. It should be noteworthy that the eutectic composition is richer in SiO_2 than that found in the conditions of the transition zone and the composition is enriched in SiO_2 under further increase of depth. Melting experiments were extended to the core materials. It was demonstrated that SiO_2 component dissolves into molten iron from silicate melts at pressures higher than 15 GPa and the dissolution is enhanced by the increasing pressure. It was shown that potassium, a possible candidate as heat source in the core, also dissolves into molten iron. These results make it possible to construct a core formation model which consistently account for the light elements of the outer core, and the evolution of the core and the formation of the D^1 layer associated with cooling of the earth. Less

对Mg_2SiO_4-Fe_2SiO_4系统，绘制了橄榄石改性尖晶石-尖晶石相变和尖晶石后相变的详细相图。地幔尖晶石在小于4km的深度范围内解离成钙钛矿（Pv）和镁橄榄石（Mw），使650 km的不连续面变得尖锐。这一特征提供了650 km深度地幔温度的固定点，并提出了上地幔温度的标准剖面。分析了下降板的动力特性。深源地震的特征很好地解释了由相位边界的扭曲引起的作用在板片上的下沉力和浮力。在25 GPa和2000 ℃条件下对MgCO_3和MgCO_3-MgSiO_3体系进行的亚固相线和熔融实验结果表明，MgCO_3-MgSiO_3体系在700 km深度附近的地震活动突然消失，可能是由于Pv和Mw的破裂组合所引起的超塑性。 ...更多信息当深度大于140 km时，CO_2不再以挥发性组分的形式存在，而是以菱镁矿的形式固定下来，并通过岩浆作用逐渐释放到大气中。CO_2在高温高压下在H_2O流体中溶解度的测定，使得从俯冲作用的角度讨论CO_2的再循环过程成为可能，下地幔物质的熔融关系也受到了广泛关注。MgSiO_3Pv在2500 ℃和23 GPa下全等熔，dTm/dP斜率约为25 μ m/GPa。MgO-FeO-SiO_2系的熔化关系在Pv和Mw之间表现为共晶熔化。值得注意的是，共晶成分比过渡区条件下的成分更富SiO_2，且随着深度的进一步增加，共晶成分更富SiO_2。熔化实验扩展到芯材。实验结果表明，在高于15 GPa的压力下，SiO_2组分从硅酸盐熔体中溶解到铁液中，并且随着压力的增加，SiO_2组分的溶解增强。结果表明，钾，一个可能的候选人作为热源的核心，也溶解到熔融铁。这些结果使得构建一个核心形成模型成为可能，该模型一致地解释了外核的轻元素、核心的演化以及与地球冷却相关的D^1层的形成。少