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

OCE-0752478，OCE-0752669智力上的优点：位于大洋板块内部(例如，克尔盖伦、留尼汪岛、加拉帕戈斯)的相当多的热点(据信与从地球地幔涌出的岩浆上涌有关的海底火山的集中)似乎直接影响到位于板块边界的大洋中脊发现的玄武岩的化学，在热点和海脊近端产生的玄武岩的化学成分以及沿海脊异常的地壳厚度似乎都证明了这一点。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。该项目将使用一种多学科建模方法来表征离轴热点-山脊系统中的地幔流动和熔融，其中熔融模型与数值地球动力学模型相耦合，以便能够预测熔体化学。所产生的耦合模型将特别应用于Easter-Salas y Gomez海山链-EMP系统，使用合成熔体成分以及模型预测的地球物理参数(例如地壳厚度、重力)，通过与观测数据的直接比较来限制地幔流动。ESC-EMP系统是研究热点和附近大洋中脊相互作用的理想天然实验室：ESC-EMP系统的几何结构简单，沿热点和扩张中心之间的ESC部分存在最近的火山活动，并且该地区已经存在一个全面的地球化学数据库。该项目由两项主要任务组成。第一个任务是对现有的地球化学数据进行建模，以约束与ESC-EMP系统相关的源和熔融参数。这些结果将被合并到热点-山脊系统的三维地球动力学模型中，以研究ESC-EMP系统中的地幔流动。然后，地球动力学模型预测(例如，熔体化学、地壳厚度、重力的空间变化)将与观测数据进行比较，以约束Easter-Salas y Gomez热点的温度和成分，以及物质从热点流向山脊轴的方式(即径向弥散与槽状流动)。作为地球动力学模拟工作的一个副产品，将开发一系列与地幔流动有关的3-D基准测试，并将其应用于两个数值模拟包：这项提议概述的内在跨学科方法，将地球化学与地球动力学模拟结合起来，将有助于首席研究员的专业发展，他们都是新近获得博士学位的。该项目还将为波士顿大学的一名研究生提供资金，该研究生在霍尔的建议下，将与金斯利进行广泛的互动，从他们职业生涯的一开始就为这名学生提供一个在地球动力学和地球化学之间的界面工作的绝佳机会。与上地幔有关的自由对流和强迫对流情况模型的基准结果将通过出版物和在线文件向广大社区提供。此外，更简单的基准情景将成为霍尔与波士顿大学教授塞尔吉奥·费格拉齐共同开发的关于地球科学中计算流体动力学的高级本科生/研究生入门课程的组成部分。此外，霍尔将利用该项目的结果作为案例研究，突出多学科方法来了解地球内部，在他将在波士顿大学教授的本科地球动力学课程中。最后，为模拟熔融和预测熔融化学以及对这些结果进行后处理而开发的算法将通过位于BU的网站提供给社区，也可能通过地球动力学计算基础设施(CIG)计划提供

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