CSEDI Collaborative Research: Understanding the origins of MORB geochemical heterogeneity using constraints from seismic tomography and geodynamic modeling

在大洋中脊的水下喷发的熔岩的化学成分受到产生这些熔体的下地幔的温度和成分的影响，在那里，随着构造板块的分散，新的海底被创造出来。这项拟议的工作检查了大洋中脊玄武岩(MORB)化学成分与地震层析成像产生的地球内部图像之间的相关性。它使用大规模的地幔流动数值模型，将地表观测与过去和现在的地幔结构联系起来。拟议的工作有三个组成部分。首先，它研究了氦同位素和其他指示地幔温度的地球化学指标在扩张中心的分布，以及它们与海底地幔的温度和成分变化的关系。其次，它探索了在扩张中心取样的地幔物质的流动历史。第三，它阐述了自超大陆盘古大陆解体以来，不同洋盆中的大洋中脊是如何采样地幔的。该项目将提供关于海洋盆地下地震速度的变化如何与MORB化学成分的变化有关的新信息，以及上地幔成分和温度的变化如何与更深的地幔结构有关的新信息。不同的学科对我们理解地幔的动力学做出了不同的贡献。特别是，将地球化学和地震学的非均质性在全球范围内的分布联系起来一直是一项挑战，因为这两种方法的采样波长不同：局部的，用于地球化学的，长波长的，用于地震学的。最近，这两个领域都取得了进展，全球地震层析成像的分辨率达到了1000公里以下，大洋中脊沿线进行了更完整的地球化学采样，从而能够在与地震成像相称的波长上调查模式。与此同时，在结合地震学和地表观测(例如，板块运动、地形和大地水准面)的约束条件下，在开发三维地幔环流的现实地球动力学模拟方法方面取得了进展。将这些元素捆绑在一起，以更好地约束在山脊上取样的材料的流动历史，目前是可行的。这项拟议的工作将产生新的地球化学数据集、层析模型和地球动力学模型的结果，这些数据将分发给更广泛的地球科学界进行进一步分析，并以一种允许身临其境的3D可视化的格式进行分析。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The chemical composition of lavas erupted under the water at mid ocean ridges, where new seafloor is created as tectonic plates spread apart, is influenced by the temperature and composition of the underlying mantle from which these melts are generated. The proposed work examines correlations between mid ocean ridge basalt (MORB) chemistry and images of Earth's interior produced using seismic tomography. It uses large-scale numerical models of mantle flow to connect surface observations with past and present mantle structure. The proposed work has three components. First, it examines the distributions of helium isotopes and other geochemical indicators of mantle temperature at spreading centers and how these are related to temperature and compositional variations in the sub-oceanic mantle. Second, it explores the flow history of mantle material that is sampled at spreading centers. Third, it addresses how the mid ocean ridges in different ocean basins have sampled the mantle since the breakup of the supercontinent Pangea. The project will provide new information about how variations in seismic velocity beneath the ocean basins are related to the variations in chemical composition of MORB, and how upper mantle variations in composition and temperature are related to deeper mantle structure.Different disciplines make distinct contributions to our understanding of the dynamics of Earth's mantle. In particular, relating the distribution of geochemical and seismological heterogeneity at the global scale has been a challenge because of the different wavelengths sampled in these two types of approaches: local, for geochemistry, long wavelength, for seismology. Recently, progress has been made in both fields, with resolution reaching sub-1000 km scale in global seismic tomography, and a more complete geochemical sampling along mid-ocean ridges, allowing the investigation of patterns at wavelengths commensurate with the seismic imaging. Concurrently, progress has been made in developing methodologies for realistic geodynamic modeling of mantle circulation in 3D, incorporating constraints from seismology and surface observables (e.g. plate motions, topography, and the geoid). Tying these elements together to better constrain the flow history of material sampled at ridges is becoming feasible at the present time. The proposed work will produce new geochemical datasets, tomographic models, and results from geodynamic models that will be distributed to the broader geoscience community for further analysis and in a format that permits immersive 3D visualization.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.