RII Track-4: Investigating the Effects of Faulting on Chemical Exchange Between Seawater and Earth’s Mantle at Slow Mid-Ocean Ridges

RII Track-4：研究断层对慢洋中脊海水与地幔之间化学交换的影响

• 批准号: 2033364
• 负责人: Timothy Schroeder
• 金额: $ 15.35万
• 依托单位: Bennington College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-02-01 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2033364&HistoricalAwards=false
• 关键词: RII; Track; Investigating; Effects; Faulting

The mid-ocean ridge system is a 65,000 km-long mountain range that wraps around the Earth at the center of each ocean basin. New tectonic plate is continuously generated along the ridges at rates of one to 20 cm per year. Global seawater composition, and thus Earth’s climate, is maintained over geologic timescales by a balance between chemical-exchange reactions that occur when seawater infiltrates into hot rock at mid-ocean ridges, and salts flowing into the ocean from continental rivers systems. Mantle rock has a radically different chemical and mineral composition than crustal rock, and the nature of its chemical interactions with seawater, along with the larger implications for seawater composition, are poorly understood. The goal of this proposal is to build understanding of the processes by which seafloor mantle-rock exposures are fractured to permit seawater infiltration, and thus facilitate water-rock chemical exchange on roughly half of the global mid-ocean ridge system. Results from this study will be integrated in the undergraduate Earth Science courses and independent research projects for undergraduate students at Bennington College, a small liberal arts institution.The goals of this project are to understand how pre-existing ductile deformation fabrics and the tectonic environment of mantle peridotite exposures control the process by which rock permeability is generated during brittle fracturing. Rock samples collected from three mantle peridotite exposures along the Mid-Atlantic Ridge (MAR) that formed by very different types of fault zones will be examined using several distinct microanalysis and imaging techniques: 1) micro-computed tomography and scanning electron microscope imaging will be used to characterize the micro-scale geometry of fracture networks, 2) thermogravimetric analysis and helium gas pycnometry will be used to quantify the degree of hydrothermal alteration and 3) confocal Raman spectroscopy will be used to place additional constraints on the nature of hydrothermal exchange with micro-analysis of alteration minerals and trapped fluids. Rock samples will be obtained from collections at Woods Hole Oceanographic Institution and from the Bremen Core Repository in Bremen, Germany. The outcomes of this research will have broad applications to understanding the deep biosphere, and potential origins of life on Earth as well as potential hosts for life on other planets.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.

大洋中脊系统是一个长达 65,000 公里的山脉，在每个海洋盆地的中心环绕地球。新的构造板块沿着洋脊以每年 1 至 20 厘米的速度不断生成。因此，地球气候在地质时间尺度上是通过海水渗入洋中脊热岩和盐流入洋中脊时发生的化学交换反应之间的平衡来维持的。大陆河流系统的海洋具有与地壳岩石截然不同的化学和矿物成分，人们对它与海水的化学相互作用的性质以及对海水成分的更大影响知之甚少。旨在了解海底地幔岩石暴露破裂以允许海水渗透的过程，从而促进全球大约一半的洋中脊系统的水-岩石化学交换。这项研究的结果将纳入本科生课程。地球本宁顿学院是一所小型文科院校，为本科生提供科学课程和独立研究项目。该项目的目标是了解预先存在的延性变形结构和地幔橄榄岩暴露的构造环境如何控制岩石渗透性的过程。将从沿大西洋中脊 (MAR) 的三个地幔橄榄岩暴露区收集的岩石样本（由非常不同类型的断层带形成）将使用几种不同的微分析和方法进行检查。成像技术：1）微型计算机断层扫描和扫描电子显微镜成像将用于表征裂缝网络的微观几何形状，2）热重分析和氦气比重测定将用于量化热液蚀变程度，3）共焦拉曼光谱将用于对蚀变矿物和从伍兹霍尔收集的捕获流体进行微观分析，对热液交换的性质施加额外的限制。海洋学研究所和德国不来梅核心储存库的这项研究成果将在了解深层生物圈、地球上潜在的生命起源以及其他行星上的潜在生命宿主方面具有广泛的应用。该奖项反映了美国国家科学基金会的贡献。法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。