Tracing lithium enrichment in the McDermitt caldera system by melt/fluid inclusions and in situ oxygen isotopes

通过熔体/流体包裹体和原位氧同位素追踪麦克德米特破火山口系统中的锂富集

• 批准号: 2147164
• 负责人: Philipp Ruprecht
• 金额: $ 32.51万
• 依托单位: Board of Regents, NSHE, obo University of Nevada, Reno
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2147164&HistoricalAwards=false
• 关键词: Tracing; lithium; enrichment; McDermitt; caldera

This project aims to study how lithium concentrates during supergiant volcanic eruptions, eventually forming lithium ore deposits. Lithium is a critical element that is essential to support the rapid development of rechargeable batteries used by electric vehicles and to mitigate the impacts of climate change. Understanding the mechanisms of lithium transfer in the Earth’s crust is therefore of great importance to address the global demand for lithium. This research project will study the McDermitt volcanic caldera (Nevada/Oregon) which hosts one of the most important lithium deposits in the United States. By studying microscopic inclusions of solidified silicate melts trapped in volcanic rocks (“melt inclusions”), Drs. Harlaux and Ruprecht will determine the chemical composition of the magmas that generated a catastrophic eruption at McDermitt about 16 million years ago. This research work will help to better understand how magmas become enriched in lithium and can produce high-temperature lithium-rich vapors during magma outgassing, eventually forming lithium deposits after collapse of the caldera floor. A doctoral student at the University of Nevada, Reno, will conduct the research project with students from underrepresented demographic groups in STEM specifically encouraged to apply. Results will also be shared through public outreach activities with a broader audience. This project will benefit directly to Nevada’s economy and to society in general for investigating the mineralization potential for lithium in other volcanic calderas in the western United States.The geochemical cycle of lithium (Li) in the Earth’s crust yielding the formation of Li-bearing clay deposits hosted in volcanic calderas is at the center of this project. Enrichment of Li in caldera-forming systems is thought to result from either magma fractionation followed by degassing of Li-rich magmatic fluids possibly mixing with meteoric groundwaters, or remobilization of Li during post-magmatic leaching of volcanic glasses by meteoric fluids without hydrothermal contribution. Considering that most volcanic calderas are not mineralized with Li, the question arises whether leaching of volcanic rocks by meteoric water alone is sufficient, or Li-rich hydrothermal fluids are required to provide sufficient Li for the subsequent formation of intracaldera Li clay deposits. This research project will focus on the McDermitt volcanic caldera (Nevada/Oregon) that produced voluminous evolved peralkaline and peraluminous magmas and Li-bearing clays that formed after the caldera collapse. By studying melt and fluid inclusions hosted in igneous phenocrysts from diverse Miocene volcanic rocks (ca. 16.7-16.0 Ma) exposed in the McDermitt caldera, Drs. Harlaux and Ruprecht will determine how Li is progressively enriched in the silicate magmas and partitioned into the magmatic volatile phase during magma outgassing and cooling of the magmatic system. The in-situ chemical and isotopic composition of melt inclusions and the host quartz phenocrysts will be analyzed by EPMA and LA-ICP-MS for major and trace elements, respectively, and SIMS for oxygen isotopes. This analytical work will allow to investigate Li enrichment during the long-lived (ca. 1 Ma) lifetime of the McDermitt magmatic system and the remobilization of Li by hydrothermal fluids released through the caldera floor and along its margins during magma degassing immediately after collapse.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.

该项目旨在研究锂在超大型火山喷发过程中如何浓缩，最终形成锂矿床。锂是支持电动汽车充电电池快速发展和缓解气候变化机制影响所必需的关键元素。因此，地壳中的锂转移对于解决全球对锂的需求非常重要。该研究项目将研究麦克德米特火山口。 （内华达州/俄勒冈州）拥有美国最重要的锂矿床之一，通过研究火山岩中凝固硅酸盐熔体的微观包裹体（“熔体包裹体”），Harlaux 和 Ruprecht 博士将确定其化学成分。大约 1600 万年前在麦克德米特发生灾难性喷发的岩浆将有助于更好地了解岩浆如何富含锂。岩浆逸气过程中会产生高温富含锂的蒸气，最终在火山口底部塌陷后形成锂沉积物，内华达大学里诺分校的一名博士生将与来自 STEM 中代表性不足的人口群体的学生一起开展这项研究项目。还将通过公共宣传活动与更广泛的受众分享结果，该项目将直接惠及内华达州的经济和整个社会，以调查其他火山中的锂矿化潜力。美国西部的火山口。地壳中锂 (Li) 的地球化学循环导致火山口火山口中含锂粘土矿床的形成，这是该项目的核心。火山口形成系统中锂的富集被认为是该项目的核心。可能是由于岩浆分馏，然后对可能与大气地下水混合的富锂岩浆液进行脱气，或者是在岩浆浸出过程中锂的再活化造成的。考虑到大多数火山口没有被锂矿化，问题是仅靠大气水淋滤火山岩就足够了，还是需要富含锂的热液流体为后续提供足够的锂。该研究项目将重点关注产生火山口内锂粘土矿床的麦克德米特火山口（内华达州/俄勒冈州）。通过研究麦克德米特火山口暴露的不同中新世火山岩（约 16.7-16.0 Ma）中的熔体和流体包裹体，发现了火山口塌陷后形成的大量演化过碱性和过铝质岩浆以及含锂粘土。鲁普雷希特将确定锂如何在硅酸盐岩浆中逐渐富集，在岩浆释气和岩浆系统冷却过程中，它们被分成岩浆挥发相。熔体包裹体和基质石英斑晶的原位化学和同位素组成将分别通过 EPMA 和 LA-ICP-MS 进行主量元素和微量元素的分析。 ，以及氧同位素的 SIMS。这项分析工作将有助于研究麦克德米特岩浆系统和岩浆系统的长寿命（约 1 Ma）期间的 Li 富集。崩塌后岩浆脱气过程中释放的热液对锂的再激活反映在火山口底部及其边缘。该奖项授予美国国家科学基金会的法定使命，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。