Numerical Models for Melt Segregation

这个项目涉及与熔化有关的物理过程 以及这些过程如何影响 喷发熔岩的地球化学性质。 这是一个自然 早期地幔对流工作的扩展， 丰富的地球化学数据来约束和检验 地幔动力学的各个方面，但为了有效地 使用这些数据，首先必须了解熔体与它们的 物理和化学的地幔源。 二维 有限元数值代码将被用来研究一个层次的 涉及熔化和熔体偏析的两相流模型：（i） 熔体偏析和微量元素分馏从化学 具有空间可变熔化程度的均匀源。 的 目的是说明和理解复杂性，包括 时间依赖性，在微量元素浓度的 “熔体”从这样的源分离。 (ii)熔体偏析和 从化学和生物学上都具有异质性的来源混合， 熔化的程度。 该模型将应用于时间 夏威夷熔岩的地球化学性质， 一种用于对源的熔体偏析进行建模的框架， 普遍存在的异质性，这似乎是由 近海脊海山的地球化学 (iii)熔化模型 以及南极海脊下的熔体迁移。 这种模式将 用于研究地壳厚度和主要 元素化学对铺展速率非常不敏感， 微量元素比值和同位素比值的变异性是 与传播速度有关。 有多少融化的问题 喷发，而不是底托否则耗尽 还考虑了岩石圈。

This project addresses physical processes associated with melting and melt segregation in the mantle, and how these processes affect the geochemical properties of erupted lavas. It is a natural extension of earlier work on mantle convection in that there is a wealth of geochemical data with which to constrain and test various aspects of mantle dynamics, but in order to effectively use this data one must first understand how melts relate to their mantle source both physically and chemically. A two-dimensional finite element numerical code will be used to study a hierarchy of two-phase flow models involving melting and melt segregation: (i) Melt segregation and trace element fractionation from a chemically uniform source with spatially variable degree of melting. The purpose is to illustrate and understand the complexity, including time dependence, of the trace element concentrations in the "melts" segregating from such a source. (ii) Melt segregation and mixing from a source having heterogeneity in both chemistry and degree of melting. This model will be applied to the time dependent geochemical properties of lavas from Hawaii and also as a framework for modeling melt segregation for a source with ubiquitous heterogeneities, as seems to be required by the geochemistry of near-ridge seamounts. (iii) Models for melting and melt migration under midocean ridges. This type of model will be used to study the implications of crustal thickness and major element chemistry being quite insensitive to spreading rate while the variability of trace element ratios and isotopic ratios is related to the rate of spreading. The questions of how much melt erupts as opposed to underplating the otherwise depleted lithosphere is also considered.