Improved Constraints on Mantle and Crustal Source Signals in CO2 well gases: New Insights from Ultra-high Precision Noble Gas and Clumped Isotope Measurements

挥发性元素（如碳、氮、氧、水和其他气体）对地球上的生命至关重要。但是，关于地球是如何形成的，挥发性元素的起源，以及它们如何在大气、海洋和地球深处之间移动，仍然有许多悬而未决的问题。通过研究从地球内部释放的气体，我们可以更多地了解挥发性元素的原始来源。不同的挥发性来源会有不同的化学特征——类似于指纹。其中一些化学特征可能在地球历史的大部分时间里都保存在地幔深处。在这个研究项目中，研究人员将使用新的分析技术来研究来自地幔的气体组成，重点是来自澳大利亚和科罗拉多高原的岩浆二氧化碳井的样本。该团队还希望深入了解二氧化碳如何储存在地下，这可以帮助我们应对大气中二氧化碳含量的增加和气候变化。二氧化碳气体在地球地下的自然运动可以为我们如何长期有效地储存二氧化碳提供线索。在澳大利亚的油田，岩浆二氧化碳气体被重新注入地下，以研究长期的地质储存是否是解决大气中二氧化碳水平上升的可行工具。该项目还将为本科生提供机会，使他们在科学研究的各个方面获得经验，如实地考察、实验室工作、建模和数据分析。过去对科罗拉多高原二氧化碳井气体中稀有气体的测量，为地幔中挥发性物质的循环提供了重要的限制。惰性气体由于其化学和生物惰性，是非常保守的来源和过程示踪剂。对二氧化碳井气样品中Ar、Kr和Xe同位素的高精度测量——比以前的测量精度高10到100倍——将为挥发循环的时间和大气中重惰性气体的宇宙化学起源提供新的线索。对这些系统中团块N2和CH4的最新技术测量将提供前所未有的关于形成温度和挥发物来源的见解，这将有助于理解深层氮向大气的再循环，以及解开热液系统中生物和非生物甲烷产生的纠缠。与澳大利亚从事二氧化碳封存项目的同事合作，在测试注入之前和之后进行的稀有气体同位素测量将被用作注入二氧化碳地下运输的新型示踪剂，可能对监测全球其他封存地点产生影响。在这项研究中进行的新测量将通过一系列同行评审的出版物、会议报告与更广泛的社区分享，并将通过在线数据库免费向公众提供。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Volatile elements (like carbon, nitrogen, oxygen, water, and other gases) are critical for life on Earth. But there are still many open questions about how Earth formed, where volatile elements originated from, and how they move between the atmosphere, oceans, and Earth’s deep interior. By studying the gases that are released from inside Earth, we can learn more about the original sources of volatile elements. Different volatile origins will have different chemical signatures – akin to a fingerprint. Some of these chemical signatures may have been preserved deep within Earth's mantle for most of Earth’s history. In this research project, researchers will use new analytical techniques to study the composition of gases from Earth's mantle, focusing on samples from magmatic carbon dioxide (CO2) wells in Australia and the Colorado Plateau. This team also hopes to gain insight into how carbon dioxide can be stored underground, which could help us combat increasing levels of CO2 in the atmosphere and climate change. The natural movement of CO2 gas through Earth's subsurface can provide clues about how we can store CO2 effectively over long periods of time. In the Australian field site, magmatic CO2 gas is being re-injected into the ground to study whether long term geological storage is a viable tool to tackling rising atmospheric CO2 levels. This project will also provide opportunities for undergraduate students to gain experience in various aspects of scientific research such as fieldwork, laboratory work, modeling, and data analysis. Past measurements of noble gases in CO2 well gases in the Colorado Plateau provide important constraints on the cycling of volatiles within Earth’s mantle. Owing to their chemical and biological inertness, noble gases are exceptionally conservative tracers of sources and processes. New high-precision measurements of Ar, Kr, and Xe isotopes in CO2 well gas samples – made at 10 to 100 times higher precision than was previously attainable – will shed new light on the timing of volatile cycling and the cosmochemical origin of heavy noble gases in our atmosphere. Novel state-of-the-art measurements of clumped N2 and CH4 in these systems will provide unprecedented insight into the formation temperature and sources of volatiles, which will aid in understanding the recycling of deep nitrogen to the atmosphere and in disentangling biotic from abiotic methane production in hydrothermal systems. In cooperation with colleagues working on CO2 sequestration projects in Australia, measurements of noble gas isotopes made before, and after, test injection will be utilized as a novel tracer for subsurface transport of injected CO2, with possible implications for monitoring other sequestration sites worldwide. The new measurements made in this study will be shared with the broader community through a series of peer-reviewed publications, conference presentations, and will be made freely available to the public through online data repositories.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.