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巨人火山喷发期间的浓缩，最终形成锂矿石沉积物。锂是一个关键元素，对于支持电动汽车使用的可充电电池的快速开发以及减轻气候变化的影响至关重要。因此，了解地壳中锂转移的机制对于解决全球对锂的需求至关重要。该研究项目将研究McDermitt火山火山口（内华达州/俄勒冈州），该火山口是美国最重要的锂矿床之一。通过研究被困在火山岩中（“熔体夹杂物”）中的固化有机硅熔体的微观夹杂物，Drs。 Harlaux和Ruprecht将确定大约1600万年前在麦克德米特（McDermitt）造成灾难性喷发的岩浆的化学成分。这项研究工作将有助于更好地了解岩浆如何在锂中富集，并在岩浆量中产生高温富含锂的蒸气，最终在Caldera地板倒塌后形成锂沉积物。内华达州内华达大学的一名博士生将与来自STEM中代表性不足的人群的学生专门申请。结果也将通过公共外展活动与更广泛的受众共享。该项目将直接受益于内华达州的经济和整个社会，以调查美国西部其他火山火山口中锂的矿化潜力。地球上锂的地球化学循环（li）产生了在该项目的中心。人们认为，在火山口形成系统中富集Li是由于岩浆分馏而导致的，然后脱气，含量富含Li的岩浆流体可能与流星地下水混合，或者在通过无水热贡献的气象杯中杂乱无章的火山玻璃行走时将LI的液化化。考虑到大多数火山火山口没有用LI矿化，因此出现的问题是仅凭流星水对火山岩的领先地位是足够的，或者需要富含液体的水热壶以提供足够的LI来为随后形成的核内clay粘土沉积物的形成。该研究项目将重点关注麦克德米特火山火山口（Nevada/Oregon），该火山口（内华达州/俄勒冈州）产生了大量进化的paralline和peraluminuines岩浆和含液的粘土，并在火山口倒塌后形成。通过研究中新世火山岩（Ca. 16.7-16.0 mA）中托管的熔体和流体夹杂物，在麦克德米特·瓦尔德拉（McDermitt Caldera）中暴露于博士。 Harlaux和Ruprecht将确定Li如何逐渐富集在硅胶岩浆中，并在岩浆系统的岩浆和冷却过程中划分为岩浆挥发阶段。 EPMA和LA-ICP-MS将分别分析主要和痕量元素的熔体夹杂物和宿主石英表晶的原位化学和同位素组成，以及氧同位素的SIMS。这项分析工作将允许在McDermitt Magmatic系统的长寿（1 Ma）寿命（约1个MA）期间调查LI富集，并通过Caldera地板上释放的水热液和岩浆脱胶期间的边缘脱落的水热流体对LI进行重新启动，这是NSF裁定的良好及其在NSF的稳定范围内的稳定性。 标准。