CAREER: Partitioning of Rare Earth Elements (REE) Between Minerals and Aqueous Fluids in Ore Deposits

稀土元素（REE）具有相似但略有不同的离子半径和原子质量，这允许研究化学元素的基本行为及其在自然系统中的矿物结构中的结合。它们的磁性使它们成为风力涡轮机、混合汽车电池和节能灯中磷光体中使用的永磁体的重要组成部分。矿物的稀土元素组成也被用于地球科学，以追踪地壳中的地质过程。矿床通常通过金属在含水流体中的活动和热液脉中的矿化在深部形成。流体和矿物的性质将影响不同稀土元素的分馏。目前，我们有很多关于如何系统地量化矿物的微量元素特征与流体-岩石相互作用和成矿过程的探索。该CAREER建议通过实验室实验，数值模拟和天然矿物中捕获的流体包裹体来探索矿床中含水流体和矿物之间的REE断裂。THERMO流体项目将开始为本科生准备流体矿物暑期学校，开放获取小册子和专用的热力学实践教程网页。该项目的一个主要目标是提供一个教育平台，并展示热力学在地球科学中的更广泛意义。方解石、萤石、磷灰石是稀土矿床中常见的脉石矿物。这些矿物记录了地球化学特征，可用于确定与成矿过程相关的温度、流体化学和潜在流体通道。这项研究涉及在100至350摄氏度下进行的一系列综合热液实验，用于确定REE在含水流体-方解石、-磷灰石和-萤石之间的分配，作为温度和流体组成的函数（即，盐度、pH和配体活性）。实验数据将用于开发一种新的热力学模型，用于预测和量化这些热液矿物中的REE特征。为了测试该模型，将在北美过碱性、碳酸盐岩和氧化铁-磷灰石矿床中研究一组矿物微量元素成分和流体包裹体。拟议研究的目标是提供一个框架，用于模拟矿床中与流体-岩石反应相关的痕量金属的分配，并提高我们建模和解释成矿过程的能力。该奖项反映了NSF的法定使命，并被认为值得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来支持。

The rare earth elements (REE) have similar but slightly different ionic radii and atomic masses, which permits studying the fundamental behavior of chemical elements and their incorporation in mineral structures in natural systems. Their magnetic properties make them important components in permanent magnets used in wind turbines, batteries of hybrid cars, and phosphors in energy efficient light. The REE composition of minerals is also used in geosciences to trace geological processes in the Earth's crust. Ore deposits commonly form at depth through the mobilization of metals in aqueous fluids and the mineralization in hydrothermal veins. The properties of both, the fluid and the minerals, will affect how the different REE are fractionated. Currently, we have much to discover about how to quantify systematically the trace element signatures of minerals with regards to fluid-rock interaction and ore-forming processes. This CAREER proposal explores how REE fractionate between aqueous fluids and minerals in ore deposits using laboratory experiments, numerical modeling and fluid inclusions trapped in natural minerals. The THERMO fluids project will be initiated with the preparation of a Fluids & Minerals summer school for undergraduate students, an open access booklet, and a dedicated hands-on thermodynamics tutorial webpage. A major aim of this project will be to provide an education platform and demonstrate the broader significance of thermodynamics in geosciences. Calcite, fluorite and apatite are common gangue minerals associated to REE and other mineral deposits. These minerals record geochemical signatures that may be used to determine temperature, fluid chemistry and potentially fluid pathways associated to ore-forming processes. This research involves a comprehensive series of hydrothermal experiments at 100 to 350 degrees C for determining the partitioning of REE between aqueous fluid-calcite, -apatite and -fluorite as a function of temperature and fluid composition (i.e., salinity, pH and ligand activity). The experimental data will be used to develop a new thermodynamic model for predicting and quantifying REE signatures in these hydrothermal minerals. To test the model, a set of mineral trace element compositions and fluid inclusions will be studied in peralkaline, carbonatite, and iron oxide-apatite hosted ore deposits in North America. The objective of the proposed research is to provide a framework for simulating the partitioning of trace metals associated to fluid-rock reactions in ore deposits and advance our capabilities of modeling and interpreting ore-forming processes.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.