Layering processes in the evolution of planetary mantle

行星地幔演化的分层过程

• 批准号: 252309337
• 负责人: Professor Dr. Ulrich Hansen
• 金额: --
• 依托单位: Institut für Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/252309337?language=en
• 关键词: Layering; processes; evolution; planetary; mantle

Layer formation is a prominent feature in many natural systems. Distinct layers are stacked and separated by sharp interfaces. They are on the scale of magma chambers and intrusions or on grandeur dimension; the Earth's oceans and the mantle of planetary bodies. The internal structure of the Earth's mantle, i.e. the separation of the upper and lower mantle, has always been and remains highly debated and the presence of additional layers is considered to be likely, despite a still missing proof. Pure thermal convection is not sufficient to generate separately convecting layers. It has been assumed that the endothermic phase change from spinel to perovskite at a depth of 670km is a potential mechanism to separate the convective flows in the upper and lower mantle. But considering earth-like conditions early numerical studies showed, that complete layering is not expected for geological timescales. Taking into account at least two components that influence the density and have different diffusivities, distinct layers can evolve dynamically. Such systems are called double diffusive systems (d.d.c). Identifying one component as heat and the other as chemical composition (e.g. heavy material) it seems to be likely that d.d.c. plays a significant role in the dynamics of a planetary mantle, especially for the formation of distinct layers in the Earth's mantle.Within the scope of the submitted proposal we want to research the process of layering due to double diffusive convection and the consequences for the evolution of the Earth's mantle. The main focus of attentions is the formation and evolution of self-organised layers in the presence of an endothermic phase change. At first a pre-existing numerical double diffusive model will be improved by the effect of a phase change. Another key aspect will then be the investigation of layering with respect to an earth-relevant rheology. This will be an essential step and will help to get a better understanding for the evolution of the Earth's mantle and the today's observed surface features like plate tectonics, geochemistry, surface heat flow, etc.. To our knowledge this kind of study has never been done by any other work group.

地层形成是许多自然系统的一个显著特征。不同的层堆叠在一起，并被清晰的界面分开。它们的规模相当于岩浆库和侵入体，或者是宏伟的尺度;地球的海洋和行星体的地幔。地球地幔的内部结构，即上地幔和下地幔的分离，一直是并且仍然是高度争论的，尽管仍然缺乏证据，但认为可能存在额外的层。纯粹的热对流不足以产生单独的对流层。670 km深处尖晶石到钙钛矿的吸热相变可能是上地幔和下地幔对流分离的一种机制。但考虑到类似地球的条件，早期的数值研究表明，在地质时间尺度上，完全分层是不可能的。考虑到至少两种影响密度并具有不同扩散率的组分，不同的层可以动态地演变。这样的系统被称为双扩散系统（d.d. c）。确定一种成分为热量，另一种成分为化学成分（例如重物质）d. d.c.似乎在行星地幔的动力学中起着重要作用，特别是对于地幔中不同层的形成。在提交的提案的范围内，我们希望研究由于双重扩散对流造成的分层过程及其对地幔演化的影响。地幔。关注的主要焦点是在存在吸热相变的情况下自组织层的形成和演化。首先，一个预先存在的数值双扩散模型将被改进的相变的效果。另一个关键方面将是调查分层与地球相关的流变学。这将是一个重要的步骤，将有助于更好地了解地球地幔的演化和今天观察到的地表特征，如板块构造，地球化学，地表热流等。据我们所知，任何其他工作组从未进行过这种研究。