RUI: Collaborative Research: Constraining peridotite alteration timescales with environmental tracers (3H, 39Ar, 14C and 81Kr)

RUI：合作研究：用环境示踪剂（3H、39Ar、14C 和 81Kr）约束橄榄岩蚀变时间尺度

• 批准号: 2127532
• 负责人: Amelia Vankeuren
• 金额: $ 14.66万
• 依托单位: University Enterprises, Incorporated
• 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: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2127532&HistoricalAwards=false
• 关键词: RUI; Collaborative; Research; Constraining; peridotite

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Peridotite is the main constituent of the Earth's upper mantle. Peridotite alteration through water-rock interaction plays an important role in the global carbon budget and produces hydrogen gas (H2) that can support lifeforms fueled by chemical energy. This project will use the Samail ophiolite in Oman, the largest chunk of peridotite rock at the Earth’s surface, as a field laboratory to investigate the process of low temperature (25-60oC) peridotite alteration. Natural environmental tracers in groundwater within the ophiolite will be used to provide a maximum timescale for low temperature alteration and the source and supply rate of H2. These results will eventually help to calculate the rate of low temperature peridotite alteration and fluid flow through the ophiolite system and thus inform the use of ophiolites for geological carbon dioxide storage to combat climate change. They will also provide insight into the amount of chemical energy available to support life in this extreme hyperalkaline environment and in other locations of low temperature peridotite alteration on Earth and potentially elsewhere, like Mars. This project will be transformative in the education and training of geoscientists at two primarily undergraduate institutions: California State University, Sacramento, a minority-serving institution, and Barnard College in New York City, a women's college. The project will support student research experiences through both faculty-mentored student projects and course-based undergraduate research experiences (CUREs). CURE classroom modules will be publicly shared for use by other hydrogeology/geochemistry instructors throughout the nation. The project will also support the development of groundwater demonstration tanks to illustrate the use of environmental tracers and the impact that precipitation of secondary minerals can have on groundwater flow. The aim of this project is to use a suite of environmental tracers in the hyperalkaline (pH 11-12) groundwater of the Samail ophiolite to determine the maximum timescale of low temperature peridotite alteration and the source and supply rate of H2 gas. Groundwater samples will be collected using boreholes and sampling equipment recently installed in the mantle peridotite of the Samail ophiolite as part of the International Continental Scientific Drilling Program's Oman Drilling Project. Groundwater ages are currently unknown and estimates span several orders of magnitude. For this project, age distributions will be determined with environmental tracers 3H, 14C, stable noble gases, 39Ar and/or 81Kr. These ages will place upper bounds on the timescale of low temperature peridotite alteration and help determine if the water-rock interaction causing this alteration is taking place in the hydraulically conductive near-surface or if there are deeper, and/or older contributions. Other tracers (dissolved He and H2, 3He/4He ratios, and δ2H in H2) will be used to distinguish between several previously proposed sources of H2 in hyperalkaline groundwater: local production by low temperature water-rock interaction, transport from deeper sources, or release through weathering of fluid inclusions formed by peridotite alteration at higher temperature. Finally, the combination of groundwater ages and measured H2 concentrations will be used to quantify a minimum H2 accumulation rate in the aquifer. This H2 accumulation rate can then be used in bioenergetic calculations of the capacity to support chemosynthetic microbial life in this unique ecosystem.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.

该奖项的全部或部分资金根据《2021 年美国救援计划法案》（公法 117-2）提供。橄榄岩是地球上地幔的主要成分。通过水-岩石相互作用发生的橄榄岩蚀变在全球碳预算中发挥着重要作用，并产生氢气（H2），可以支持以化学能为燃料的生命形式。该项目将利用阿曼的萨迈伊蛇绿岩（地球表面最大的一块橄榄岩）作为现场实验室，研究低温（25-60oC）橄榄岩蚀变过程。蛇绿岩内地下水中的自然环境示踪剂将用于提供低温变化的最大时间尺度以及氢气的来源和供应率。这些结果最终将有助于计算低温橄榄岩蚀变率和蛇绿岩系统的流体流动率，从而为利用蛇绿岩进行地质二氧化碳封存以应对气候变化提供信息。他们还将深入了解在这种极端超碱性环境以及地球上和其他地方（例如火星）低温橄榄岩蚀变的其他地点可用于维持生命的化学能量的量。该项目将对两所主要本科院校的地球科学家的教育和培训产生变革：加州州立大学萨克拉门托分校（一所为少数族裔服务的机构）和纽约巴纳德学院（一所女子学院）。该项目将通过教师指导的学生项目和基于课程的本科生研究经验（CURE）来支持学生的研究经验。 CURE 课堂模块将公开共享，供全国其他水文地质/地球化学教师使用。该项目还将支持开发地下水示范池，以说明环境示踪剂的使用以及次生矿物沉淀对地下水流的影响。该项目的目的是在 Samail 蛇绿岩超碱性（pH 11-12）地下水中使用一套环境示踪剂来确定低温橄榄岩蚀变的最大时间尺度以及氢气的来源和供应率。作为国际大陆科学钻探计划阿曼钻探项目的一部分，地下水样本将使用最近安装在萨迈伊蛇绿岩地幔橄榄岩中的钻孔和采样设备采集。目前地下水年龄尚不清楚，估计值有几个数量级。对于该项目，年龄分布将通过环境示踪剂 3H、14C、稳定惰性气体、39Ar 和/或 81Kr 来确定。这些年龄将为低温橄榄岩蚀变的时间尺度设定上限，并有助于确定导致这种蚀变的水-岩石相互作用是否发生在水力传导的近地表中，或者是否存在更深和/或更古老的贡献。其他示踪剂（溶解的 He 和 H2、3He/4He 比率以及 H2 中的 δ2H）将用于区分超碱性地下水中 H2 的几个先前提出的来源：低温水-岩石相互作用产生的本地产生、来自更深来源的传输或通过橄榄岩在较高温度下蚀变形成的流体包裹体风化而释放。最后，地下水年龄和测得的 H2 浓度的结合将用于量化含水层中的最小 H2 积累率。然后，该氢气积累率可用于支持该独特生态系统中化学合成微生物生命的能力的生物能计算。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。