Crystallizing the terrestrial magma ocean: thermo- and geodynamics

陆地岩浆海洋的结晶：热力学和地球动力学

• 批准号: 276817549
• 负责人: Dr. Gerd Steinle-Neumann
• 金额: --
• 依托单位: Standort Berlin-Adlershof
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/276817549?language=en
• 关键词: Crystallizing; terrestrial; magma; ocean; thermo

Cooling and crystallization of the magma ocean that likely originated from the Moon-forming impact set the initial thermal and chemical structure of the solid mantle and thus the conditions for the subsequent evolution of the interior controlled by thermo-compositional convection. Modelling of the composition resulting from magma ocean crystallization requires a detailed description of the liquidus and phase diagram - over the entire mantle pressure-range-, of the distribution coefficients of major elements between crystals and melts, and of the density of residual liquids and newly formed solids. We will extend thermodynamic models of melting phase relations in the MgO-SiO2 system to the FeO-MgO-SiO2 (FMS) and CaO-MgO-SiO2 (CMS) systems by performing targeted multianvil high-pressure experiments. The focus will be on better constraining the liquidus on the MgSiO3 side of the eutectic in the presence of FeO and to obtain reliable data on the eutectic in the CMS system in which all major phase of the lower exists: periclase, bridgmanite and Ca-perovskite. These experiments will also be used to establish partition coefficients, in particular of Fe, between the melt and lower mantle phases. The additional constraints will be incorporated into a model of fractional crystallization of the magma ocean, establishing the crystallization sequence and the density structure of the terrestrial magma ocean. Newly obtained MD results on melt densities in the CMS, the FMS and Al2O3-bearing mantle compositions will be included to compute buoyancy of crystallizing lithologies. The resulting density stratification will provide us with a physically and chemically consistent picture of the thermal and compositional state of the mantle immediately after its solidification and will serve as a novel starting point for numerical models of the dynamics of the interior. We will employ these models to simulate the coupled evolution of the mantle and core over the entire history of the Earth and characterize from a new perspective fundamental processes such as the onset and maintenance of plate tectonics and magnetic field generation, and the formation and subsequent mixing of large scale geochemical reservoirs.

岩浆海洋的冷却和结晶可能起源于月球形成的撞击，这为固体地幔的初始热化学结构奠定了基础，从而为随后由热成分对流控制的内部演化创造了条件。对岩浆海洋结晶形成的成分进行建模，需要详细描述整个地幔压力范围内的液相图和相图，晶体和熔体之间主要元素的分布系数，以及残余液体和新形成固体的密度。我们将通过有针对性的多砧高压实验，将MgO-SiO2体系中熔融相关系的热力学模型扩展到FeO-MgO-SiO2 （FMS）和CaO-MgO-SiO2 （CMS）体系。重点将是在FeO存在的情况下，更好地限制MgSiO3侧共晶的液相，并在CMS系统中获得可靠的共晶数据，在CMS系统中，所有主要相都存在：方长石、桥锰矿和钙钛矿。这些实验还将用于建立熔体和下地幔相之间的分配系数，特别是铁的分配系数。这些附加的约束条件将被纳入岩浆海分离结晶模型，建立陆相岩浆海的结晶序列和密度结构。新获得的熔融密度MD结果将包括在CMS， FMS和含al2o3的地幔组成计算结晶岩性的浮力。由此产生的密度分层将为我们提供地幔凝固后立即的热状态和成分状态的物理和化学一致的图像，并将作为内部动力学数值模型的新起点。我们将利用这些模型来模拟整个地球历史上地幔和地核的耦合演化，并从一个新的角度来描述诸如板块构造和磁场产生的开始和维持，以及大规模地球化学储层的形成和随后的混合等基本过程。