4D physical models of migrating mid-ocean ridges: Implications for shallow mantle flow, melt distribution and seafloor topography

迁移的洋中脊的 4D 物理模型：对浅地幔流、熔体分布和海底地形的影响

• 批准号: 1635909
• 负责人: Christopher Kincaid
• 金额: $ 35.77万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1635909&HistoricalAwards=false
• 关键词: 4D; physical; models; migrating; mid

Plate tectonics and planetary convection in the form of mid-ocean ridge spreading, plate subduction and mantle plumes drive the natural mass/energy cycling of the solid earth-hydrosphere-atmosphere system over geological time scales and provides important context for present day global climate change. It is estimated that roughly half of the carbon provided to the hydrosphere/ atmosphere from magmatic processes generated by these geological drivers is attributed to plate spreading of the world's 80,000 km long mid-ocean ridge system. This project will use a physical laboratory apparatus to develop improved models of convective mantle flow driving plate motion and magmatic production beneath mid-ocean ridges by characterizing the essential processes not only in 3-dimensions but also their time evolution. Previous models that attempt to connect mantle flow, magma production and mass/energy flux to Earth's oceans/atmosphere have typically only been conducted in two-dimensions. The combination of recent geological and geophysical data and model upgrades clearly show that 2D model representations are insufficient. The project includes support for a graduate student and research opportunities for undergraduates from under-represented groups including local native american students through the Research Experience for Undergraduates program at the University of Rhode Island. Physical models will also provide a visually accessible experience of deep earth processes for university, school and public outreach audiences.This project will design and construct geodynamic models that build and expand on established and tested laboratory apparatus for exploring the essential four-dimensional processes related to mid-ocean spreading ridges. While numerical models suffer from resolution issues and are approximations to a set of governing equations with errors that are usually entirely unknown, physical models are particularly useful as they permit high resolution 3D physics with a natural time dependency in regions of interest (e.g. in the melt generation regions beneath ridges) and allow model boundary artifacts to be minimized. The project will investigate both basic ridge geometries and models with more complex attributes such as mid-ocean ridge migration and its role on upper mantle dynamics, seafloor topography, and mid-ocean ridge magmatic processes. This new lab apparatus will investigate several previously proposed but untested models: (1) asymmetric upwelling of the upper mantle below the leading tectonic plate, (2) asymmetric distribution of seamounts across migrating mid-ocean ridge systems, (3) magmatic segmentation and melt scavenging of offset mid-ocean ridges, and (4) enhanced upwelling at ridge-transform intersections. The design of the migrating ridge apparatus will allow transform offsets, spreading rates, and migration vectors that can scale to the full spectrum of known mid-ocean ridge systems. The laboratory model and suite of modeling results will provide a unique test of the 4D character of mid-ocean ridges and provide insight into geodynamic and melting processes at mid-ocean spreading centers. Results are expected to have important implications for understanding fundamental mantle processes and how these influence mass/energy fluxes to the hydrosphere/atmosphere systems on geologic time scales. These models will also provide important benchmarks for related fields, such as mantle properties, seismic tomography and estimates of absolute plate motions.

洋中脊扩张、板块俯冲和地幔柱等形式的板块构造和行星对流驱动着固体地球-水圈-大气系统在地质时间尺度上的自然质量/能量循环，并为当今全球气候变化提供了重要背景。 据估计，这些地质驱动因素产生的岩浆过程向水圈/大气层提供的碳中，约有一半归因于世界上80 000公里长的大洋中脊系统的板块扩张。 该项目将利用一个物理实验室装置，通过不仅在三维空间而且在时间演变方面描述基本过程，开发驱动大洋中脊下板块运动和岩浆生成的对流地幔流的改进模型。 以前试图将地幔流动，岩浆生产和质量/能量通量与地球的海洋/大气联系起来的模型通常只在二维空间中进行。 最近的地质和地球物理数据以及模型升级的结合清楚地表明，二维模型表示是不够的。 该项目包括通过罗得岛大学的本科生研究经验项目，为一名研究生提供支持，并为来自代表性不足群体的本科生提供研究机会，包括当地的美国土著学生。 物理模型还将为大学、学校和公共宣传受众提供直观的地球深部过程体验，该项目将设计和建造地球动力学模型，在现有和经过测试的实验室设备上建立和扩大，以探索与大洋中脊扩张有关的基本四维过程。 虽然数值模型受到分辨率问题的困扰，并且是一组具有通常完全未知的误差的控制方程的近似，但是物理模型特别有用，因为它们允许在感兴趣的区域（例如，在脊下的熔体生成区域）中具有自然时间依赖性的高分辨率3D物理，并且允许最小化模型边界伪影。 该项目将研究基本的海脊几何形状和具有更复杂属性的模型，如洋中脊迁移及其对上地幔动力学、海底地形和洋中脊岩浆过程的作用。这个新的实验室设备将研究几个以前提出但未经测试的模型：（1）领先的构造板块下方的上地幔不对称上涌，（2）迁移的洋中脊系统中海山的不对称分布，（3）偏移洋中脊的岩浆分割和熔体清除，以及（4）在脊转换交叉点增强的上涌。迁移洋脊装置的设计将允许变换偏移、扩展速率和迁移矢量，这些可以缩放到已知洋中脊系统的全部频谱。实验室模型和一套模拟结果将提供对大洋中脊4D特征的独特测试，并提供对大洋中扩张中心地球动力学和融化过程的深入了解。 结果预计将有重要的意义，了解基本的地幔过程，以及这些如何影响质量/能量通量的水圈/大气系统的地质时间尺度。 这些模型还将为地幔特性、地震层析成像和绝对板块运动估计等相关领域提供重要的基准。