Collaborative Research: A multidisciplinary study of hotspot - ridge interaction in the Easter microplate - Salas y Gomez system

OCE-0752478、oce -0752669位于海洋板块内部的大量热点（海底火山的集中，据信与来自地幔的岩浆柱上涌有关）（例如，克格伦、留尼汪、加拉帕戈斯群岛）似乎直接影响位于板块边界的洋中脊上发现的玄武岩的化学性质，热点和洋中脊近端产生的玄武岩化学性质的相似性证明了这一点。以及沿山脊的异常地壳厚度。然而，上地幔中允许这种相互作用的流动模式仍然知之甚少。该项目将利用多学科建模方法描述离轴热点脊系统的地幔流动和熔融，其中熔融模型与数值地球动力学模型相结合，从而可以预测熔融化学。所得到的耦合模型将特别应用于伊斯特-萨拉斯-戈麦斯海山链(ESC) -伊斯特微板块（EMP）系统，通过与观测数据的直接比较，将合成熔体成分与模型预测的地球物理参数（如地壳厚度、重力）一起使用，以约束地幔流动。ESC- emp系统是研究热点与附近洋中脊之间相互作用的理想的天然实验室：ESC- emp系统的几何结构简单，热点与扩张中心之间的ESC部分最近有火山活动，并且该地区已经有一个全面的地球化学数据库。该项目包括两个主要任务。第一项任务是对现有地球化学数据进行建模，以约束与ESC-EMP系统相关的源和熔化参数。这些结果将被整合到热点-脊系统的三维地球动力学模型中，以检查ESC-EMP系统中的地幔流动。然后将地球动力学模型预测（例如，熔体化学的空间变化、地壳厚度、重力）与观测数据进行比较，以限制伊斯特-萨拉斯-戈麦斯热点的温度和组成，以及物质从热点流向脊轴的方式（即，径向弥散与通道流动）。作为地球动力学建模工作的副产品，一系列与地幔流动相关的三维基准测试将被开发并应用于两个数值模拟包。更广泛的影响：本提案中概述的固有的跨学科方法，将地球化学与地球动力学建模相结合，将有助于首席研究员的专业发展，他们都是最近的博士。该项目还将为波士顿大学的一名研究生提供资金，该研究生将在霍尔的指导下与金斯利进行广泛的互动，为该学生提供一个从职业生涯的一开始就在地球动力学和地球化学之间工作的绝佳机会。与上地幔有关的自由对流和强迫对流情景的模型基准测试结果将通过出版物和在线文件向整个社区提供。此外，简单的基准情景将成为霍尔与波士顿大学教授Sergio Fagherazzi共同开发的地球科学计算流体动力学高级本科/研究生入门课程的组成部分。此外，霍尔将在波士顿大学教授的本科地球动力学课程中，将该项目的结果作为一个案例研究，强调用多学科方法来理解地球内部。最后，开发用于模拟熔化和预测熔体化学的算法，以及对这些结果进行后处理的算法，将通过波士顿大学的一个网站提供给社区，也可能通过地球动力学计算基础设施（CIG）计划提供给社区

OCE-0752478, OCE-0752669Intellectual Merit: A substantial number of hotspots (concentrations of seafloor volcanoes that are believed to be associated with upwelling plumes of magma from the Earth's mantle) that are located within the interiors of oceanic plates (e.g., Kerguelen, Reunion, Galapagos) appear to directly influence the chemistry of the basalts found at mid-ocean ridges located at the boundaries of the plate, as evidenced by similarities in the chemistry of basalts produced at the hotspot and the proximal portion of the ridge, and anomalous crustal thickness along the ridge. However, the pattern of flow in the upper mantle that would allow such interaction remains poorly understood. This project will characterize mantle flow and melting in off-axis hotspot - ridge systems using a multidisciplinary modeling approach in which melting models are coupled to numerical geodynamic models to allow prediction of melt chemistry. The resulting coupled model will be applied particularly to the Easter - Salas y Gomez Seamount Chain (ESC) - Easter Microplate (EMP) system, with synthetic melt compositions used along with model-predicted geophysical parameters (e.g., crustal thickness, gravity) to constrain mantle flow through direct comparison to observational data. The ESC-EMP system is an ideal natural laboratory for studying interaction between a hotspot and a nearby mid-ocean ridge: the geometry of the ESC-EMP system is simple, there is recent volcanism along the portion of the ESC between the hotspot and the spreading center, and a comprehensive geochemical database for the region already exists. The project consists of two primary tasks. The first task is to model the existing geochemical data to constrain source and melting parameters relevant to the ESC-EMP system. These results will then be incorporated into a 3-D geodynamic model of hotspot-ridge systems to examine mantle flow in the ESC-EMP system. Geodynamic model predictions (e.g., spatial variations in melt chemistry, crustal thickness, gravity) will then be compared to observational data to constrain the temperature and composition of the Easter-Salas y Gomez hotspot as well as the manner in which material flows from the hotspot to the ridge axis (i.e., radial dispersion vs. channeled flow) . As a byproduct of the geodynamic modeling exercise, a series of 3-D benchmark tests relevant to mantle flow will be developed and applied to two numerical modeling packagesBroader Impacts: The inherently cross-disciplinary approach outlined in this proposal, coupling geochemistry with geodynamic modeling, will contribute to the professional development of the Principal Investigators, who are both recent PhDs. The project will also provide funding for a Boston University graduate student, who, while advised by Hall, would interact extensively with Kingsley, presenting the student with an excellent opportunity to work at the interface between geodynamics and geochemistry from the very start of their career. Results of benchmarking of the models for free- and forced-convection scenarios relevant to the upper mantle will be made available to the community at large through publication and online documentation. Furthermore, the simpler benchmark scenarios will become an integral part of an advanced undergraduate/introductory graduate level course on computational fluid dynamics in the Earth sciences currently being developed by Hall, in conjunction with fellow BU professor Sergio Fagherazzi. In addition, Hall will use the results of the project as a case study highlighting a multidisciplinary approach to understanding the Earth's interior, in the undergraduate geodynamics course he will be teaching at BU. Finally, the algorithms developed to model melting and predict melt chemistry, as well as to post-process these results, will be made available to the community through a website hosted at BU and possibly also through the Computational Infrastructure for Geodynamics (CIG) program