Layering processes in the evolution of planetary mantle

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，并由尖锐的界面分开。它们的规模相当于岩浆室和侵入体，或者是宏伟的维度；地球的海洋和行星体的地幔。地球地幔的内部结构，即上下地幔的分离，一直是并仍然存在着激烈的争论，尽管仍然缺乏证据，但人们认为有可能存在额外的层。单纯的热对流不足以产生单独的对流层。认为在670 km深度从尖晶石到钙钛矿的吸热相变是分离上、下地幔对流的潜在机制。但考虑到与地球相似的条件，早期的数值研究表明，地质时间尺度不可能完全分层。考虑到至少两个影响密度和具有不同扩散系数的成分，不同的层可以动态演变。这种系统被称为双扩散系统(D.D.C.)。将一种成分确定为热，另一种确定为化学成分(例如，重质材料)，似乎很可能是DC。在行星地幔的动力学中起着重要作用，特别是在地幔不同层的形成方面。在提交的提案范围内，我们希望研究双扩散对流造成的分层过程以及对地幔演化的影响。人们关注的主要焦点是吸热相变时自组织层的形成和演化。首先，利用相变效应对已有的数值双扩散模型进行改进。然后，另一个关键方面将是关于与地球有关的流变学的分层调查。这将是至关重要的一步，有助于更好地了解地幔的演化和今天观测到的板块构造、地球化学、地表热流等地表特征。据我们所知，其他工作组从未做过这样的研究。

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.