Documenting Dynamic Accretion in the Lower Ocean Crust: Ocean Drilling Holes U1473A and 735B, SW Indian Ridge

海洋脊下岩浆房的大小、形状、矿物学、物理行为和演化决定了海洋地壳的地球化学、地球物理、热液和构造特征，海洋地壳占地球表面的70%以上（即所有发生在海底的物质）。为了更多地了解缓慢扩散的海洋地壳结构，2015-2016年，国际海洋发现计划（International ocean Discovery Program）在一个名为亚特兰蒂斯海岸的西南印度山脊上开展了一项由社区推动的重大努力，在海底岩石岩中钻深孔，来自世界各地的30多名科学家参与了这项工作。将在该奖项的支持下进行的研究分为两部分。第一部分是为789米长的岩心中300多个火成岩样本创建基础地球化学分析数据，第二部分是对离散岩心间隔进行有针对性的研究，以了解局部特征的起源。这项地层学工作的结果将与几年前从2.2公里外的海洋钻探岩心收集的类似数据进行比较。这项工作的更广泛影响包括与法国、德国、意大利和中国科学家的强有力的国际合作，支持一个了解海底成分和岩浆部分的多国科学计划，以及培养两名研究生，一名美国和一名中国，另一名由中国政府资助。将努力通过播客和专业科学传播者的参与向公众传播研究结果。实验室部分的研究包括建立全岩地球化学数据库和矿物主微量元素数据。每个样品都将进行岩石学检查，以确定矿物和结构关系，并区分原生、次生和蚀变阶段和特征。此外，利用共存的斜长石和辉石中稀土元素组成作为地温计，绘制地层剖面内各种岩浆体的化学分带剖面和热史。这些数据将构成测试假设的基础，即在亚特兰蒂斯海岸存在火成岩过程的连续性，反映了核心复合体就位的稳定状态条件。这项工作的结果可以外推，以帮助我们了解其他沿洋中脊缓慢扩散的地壳区域。

The size, shape, mineralogy, and physical behavior and evolution of magma chambers beneath ocean ridges determine the geochemical, geophysical, hydrothermal, and tectonic characteristics of ocean crust, which forms over 70 percent of Earth's surface (i.e., all that occurring under the sea). To learn more about slow-spread ocean crustal structure, a major community-driven effort to drill deep bore holes into magmatic rocks on the seafloor by the International Ocean Discovery Program and involving more than 30 scientists from around the world, was carried out in 2015-2016 on the Southwest Indian Ridge at a location called the Atlantis Bank. The research that will be carried out under the auspices of this award is divided into two parts. One part consists of creating the foundational geochemical analytical data for over 300 igneous rock specimens of the 789 meter-long core, with the second part involving targeted studies of discrete core intervals to look at the origin of local features. Results of this stratigraphic work will be compared to similar data collected from an ocean drilling core taken 2.2 kilometers away a number of years ago. Broader impacts of the work include strong international collaboration with French, German, Italian, and Chinese scientists, support of a multi-national science program to understand the composition and magmatic section of the seafloor, and the training of two graduate students, one US and one Chinese, with the second being paid for by the Chinese government. Efforts will be made to transmit findings to the public via podcasts and the participation of a professional science communicator.The laboratory part of the research consists of carrying out and creating a geochemical database of whole rock and mineral major and trace element data. Each sample will be examined petrographically to determine mineral and textural relationships and discriminate between primary, secondary, and alteration phases and features. In addition, rare earth element compositions in coexisting plagioclase and pyroxene will be used as geothermometers to develop chemical zoning profiles and thermal histories of the various magmatic bodies within the stratigraphic section. These data will form the basis for the testing of the hypothesis that there is a continuity of igneous process across the Atlantis Bank, reflecting steady-state conditions of emplacement of a core complex. Results of this work can be extrapolated to help us understand other slow-spread crustal areas along the mid-ocean ridges.