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Toward a matle GCM ; the role of the lithosphere in mantle evolution

迈向一个 matle GCM ；

基本信息

批准号：
10640401
负责人：
OGAWA Masaki
金额：
$ 1.86万
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：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640401/
关键词：
mantle convection magmatism numerical simulation plate mantle evolution Venus リソスフェア粘弾性

项目摘要

A numerical model is constructed for magmatism and mantle convection, which are the two major agents that transport heat and mass in the mantle of terrestrial planets. Special care is taken (1) to fully include the interaction between magmatism and mantle convection and (2) to realistically reproduce the lithosphere and its plate motion, the major features of mantle convection, in the numerical model. As the first step, the numerical model is constructed for Venus where the lithosphere behaves as a stagnant lid of the mantle and does not show a plate-like motion. The lithosphere is reproduced as the uppermost coldest part of the thermal boundary layer along the surface boundary, where the viscosity is much hither than the viscosity at depth in the mantle because of the strong temperature-dependence of viscosity of mantle materials assumed in the model. The numerically modeled coupled magmatism-mantle convection system episodically induces mantle overturn and the resulting extremely vigorous magmatism. The vigorous magmatism is compared to the volcanic plain formation that took place 500 to 1000 million years ago on Venus. Next, by a systematic search of parameter space for a numerical model of thermal convection with temperature-dependent viscosity, I found a convective regime where the lithosphere develops and slowly moves owing to its ductile deformation. I numerically modeled the coupled magmatism-mantle convection system on this regime, too. Now, I am improving the numerical model of plate-like motion by introducing rupture and the resulting formation of plate boundary in the lithosphere and am obtaining insights into the necessary condition for the occurrence of plate-motion on terrestrial planets. Also, I am including this improved model of plate motion in the model of coupled magmatism-mantle convection system to understand the nature of the coupled magmatism-mantle convection system in the early earth.

建立了类地行星地幔热质传递的两个主要动力-岩浆活动和地幔对流的数值模型。特别注意的是（1）充分包括岩浆活动和地幔对流之间的相互作用和（2）逼真地再现岩石圈和板块运动，地幔对流的主要特征，在数值模型。作为第一步，数值模型是为金星构造的岩石圈的行为作为一个停滞的地幔盖，并没有显示出板状运动。岩石圈被再现为沿着表面边界的热边界层的最高最冷的部分，因为在模型中假设的地幔物质的粘度的强烈的温度依赖性，在那里的粘度是远远高于在地幔中的深度的粘度。数值模拟的耦合岩浆-地幔对流系统的幕式诱导地幔翻转和由此产生的极其激烈的岩浆活动。强烈的岩浆活动被比作5亿到10亿年前发生在金星上的火山平原形成。其次，通过系统地搜索参数空间的数值模型的热对流与温度依赖的粘度，我发现了一个对流制度，岩石圈的发展和缓慢移动，由于其韧性变形。我数值模拟了这一制度的岩浆-地幔对流系统的耦合。现在，我正在通过引入岩石圈中的破裂和由此产生的板块边界的形成来改进板块运动的数值模型，并正在深入了解类地行星上发生板块运动的必要条件。此外，我还将这个改进的板块运动模型纳入到岩浆-地幔耦合对流系统模型中，以了解早期地球岩浆-地幔耦合对流系统的性质。