Structure and density of basaltic melts at mantle conditions from first-principles simulations.
Structure and density of basaltic melts at mantle conditions from first-principles simulations.
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DOI：
10.1038/ncomms9578
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发表时间：
2015-10-09
影响因子：
16.6
通讯作者：
Karki BB
中科院分区：
文献类型：
--
作者：
Bajgain S;Ghosh DB;Karki BB
深部地幔熔体的起源和稳定性，以及地球历史上不同时期的岩浆过程，都受控于组成硅酸盐液体的物理性质。在这里，我们报告基于密度泛函理论的模拟模型玄武岩，含水模型玄武岩和近MORB评估铁和水的熔体结构和密度的影响，分别。我们的研究结果表明，随着压力的增加，所有类型的主要阳离子和阴离子之间的协调强烈增加，和水的形态变化从孤立的物种扩展的形式。这些结构的变化是负责快速初始熔体致密化压缩，从而使这些玄武质熔体可能在一个或多个深度的破坏性稳定。我们的发现，熔体-水系统是理想的（几乎为零体积的混合）和混溶（负混合焓）在大多数地幔条件下加强了潜在的水富集的深地幔熔体和早期岩浆海洋的想法。 我们对深地幔熔体的起源和稳定性的理解取决于我们对硅酸盐液体组分的了解。在这里，作者模拟了铁和水对熔体结构和密度的影响，结果支持深地幔熔体和早期岩浆海洋潜在的水分富集。
The origin and stability of deep-mantle melts, and the magmatic processes at different times of Earth's history are controlled by the physical properties of constituent silicate liquids. Here we report density functional theory-based simulations of model basalt, hydrous model basalt and near-MORB to assess the effects of iron and water on the melt structure and density, respectively. Our results suggest that as pressure increases, all types of coordination between major cations and anions strongly increase, and the water speciation changes from isolated species to extended forms. These structural changes are responsible for rapid initial melt densification on compression thereby making these basaltic melts possibly buoyantly stable at one or more depths. Our finding that the melt-water system is ideal (nearly zero volume of mixing) and miscible (negative enthalpy of mixing) over most of the mantle conditions strengthens the idea of potential water enrichment of deep-mantle melts and early magma ocean. Our understanding of the origin and stability of deep-mantle melts depends on our knowledge of the component silicate liquids. Here, the authors model the effects of iron and water on melt structure and density, with results that support potential water enrichment of deep-mantle melts and an early magma ocean.