权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

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

构建了Mg_2SiO_4-Fe_2SiO_4体系的橄榄石改性尖晶石-尖晶石和后尖晶石相变的详细相图。地幔尖晶石在小于 4 公里的深度间隔内解离成钙钛矿 (Pv) 和镁方铁矿 (Mw)，使得 650 公里的不连续性变得尖锐。这一特征提供了650公里深度的地幔温度固定点，并提出了上地幔的标准温度剖面。分析了下降板块的动态特性。深源地震的特征可以通过由相界扭曲引起的作用在平板上的倾落力和浮力来很好地解释。也有人指出，700 km深度附近地震活动的突然消失可能是由于与Pv和Mw的分解组合相关的超塑性所致。对MgCO_3和MgCO_3-MgSiO_3体系在25 GPa和2000 ℃下进行的固相线和熔融实验结果表明，在深度大于140 km时，CO_2不再存在表现为挥发性成分，但以菱镁矿的形式固定，并且CO_2通过火成过程逐渐释放到大气中。高P、T条件下CO_2在H_2O流体中溶解度的考察使得考虑俯冲作用讨论CO_2的再循环过程成为可能。人们对下地幔物质的熔融关系进行了广泛的研究。 MgSiO_3 Pv 在约 2500°C 和 23 GPa 下同熔，dTm/dP 斜率约为 25°/GPa。 MgO-FeO-SiO_2体系的熔化比表现出Pv和Mw之间的共晶熔化。值得注意的是，共晶成分比过渡区条件下的共晶成分更富含SiO_2，并且随着深度的进一步增加，成分中SiO_2也更富集。熔化实验扩展到了核心材料。结果表明，在压力高于15 GPa时，硅酸盐熔体中的SiO_2成分会溶解到铁水中，并且随着压力的增加，溶解程度增强。结果表明，钾可能是地核热源的候选者，它也会溶解到铁水中。这些结果使得构建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。较少的