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A numerical simulation of mental evolution based on a two-dimentional mentle GCM

基于二维心理GCM的心理演化数值模拟

基本信息

批准号：
13640416
负责人：
OGAWA Masaki
金额：
$ 2.56万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640416/
关键词：
mantle connection plate tectonics magmatism mantle evolution numerical simulation プレート運動

项目摘要

The earlier numerical model of coupled magmatism-mantle convection system has been extended by including moving plates and the extended model of the coupled system (or mantle GCM) has been applied to the problem of mantle evolution. The numerical model suggests that the earth's mantle has evolved in two stages. On the earlier stage when the mantle is strongly heated by radioactive elements, the lower mantle are hot enough to frequently induce mantle overturn and the resulting plume activity. The magmatism induced by the plume activity makes plate motion and ridge volcanism strongly time-dependent. As the internal heating by radioactive elements becomes weaker than a threshold (the second stage), however, the mantle overturn suddenly stops and mantle convection and ridge volcanism becomes more steady. The ridge volcanism and hot spot volcanism induced by mantle overturn make the mantle chemically stratified with the deeper part of lower mantle occupied by magmatic products and the uppermost mantle occupied by residue of magma throughout the earth's history in spite of the whole mantle convection induced by subducting slabs that penetrate deep into the lower mantle. The thermal and chemical state of the numerically modeled mantle well captures the overall features of the present earth's mantle revealed by recent geochemical and seismological observation. The transition from the first to the second stage may corresponds to the Archean-Proterozoic boundary of the earth's history.

对早期的岩浆-地幔对流耦合系统的数值模型进行了扩展，引入了运动板块，并将扩展的耦合系统模型（或称地幔GCM）应用于地幔演化问题。数值模型表明，地球的地幔演化经历了两个阶段。在地幔被放射性元素强烈加热的早期阶段，下地幔的温度足以频繁地诱发地幔翻转和由此产生的地幔柱活动。地幔柱活动引起的岩浆作用使板块运动和洋脊火山作用具有强烈的时间依赖性。然而，当放射性元素的内部加热变得弱于阈值（第二阶段）时，地幔翻转突然停止，地幔对流和洋脊火山活动变得更加稳定。尽管俯冲板片深入下地幔引起了全地幔对流，但地幔翻转所引起的脊状火山作用和热点火山作用，使地幔在整个地球历史上呈现出下地幔深部为岩浆产物，上地幔为岩浆残留物的化学分层现象。数值模拟的地幔热化学状态很好地反映了现代地球化学和地震学观测所揭示的地幔的整体特征。从第一阶段到第二阶段的过渡可能对应于地球历史的太古宙-元古代界线。