Collaborative Research: Experimental Determination of REE-Chloride Complex Stability Constants and Monazite Solubilities in Hydrothermal Solutions

9705661 Wood需要在以下领域了解稀土元素在高温水溶液中的行为：1)地质年代学(即岩石测年)；2)稀土矿床地质；以及3)核废料的修复和安全储存。不幸的是，缺乏更好地了解稀土元素地球化学所需的相关数据。在许多天然溶液中，稀土与氯离子形成溶解的络合物，而稀土磷酸盐相(独居石、斜方辉石、斜方辉石)是常见的稀土矿物。因此，这项建议的目标是：1)确定独居石/磷钨矿在350(C)以下的热水溶液中的溶解度；2)确定350(C)以下的稀土氯化物络合物的化学计量和稳定性；以及3)将我们的实验数据应用于与水-岩相互作用中稀土元素的移动性有关的问题。这项研究中获得的数据将解决文献中不一致的理论估计，提供第一组高温下稀土络合物的实验热力学数据，允许对稀土氯化络合物在稀土迁移中的作用进行定量模拟，并作为改进其他稀土络合物稳定常数的理论预测的基础，直到有更多的实验数据可用。在这个项目的过程中，一名研究生和一名本科生将接受有关热液实验技术、一些现代分析方法以及与经济地质学和环境地球化学研究有关的水化学各方面的培训。此外，蒙大拿理工大学还将建立一个新的实验地球化学实验室。

9705661 Wood Knowledge of the behavior of the rare earth elements (REE) in high temperature water solutions is required in the following areas: 1) geochronology (i.e., rock dating); 2) REE ore deposit geology; and 3) remediation and safe storage of nuclear waste . Unfortunately, there is a lack of the relevant data required for a better understanding od REE geochemistry. It is expected that the REE will form a dissolved complex with the chloride ion in many natural solutions, and it is known that REE phosphate phases (monazite, xenotime, rhabdophane) are common REE minerals. Thus, the objectives of this proposal are to: 1) determine the solubility of monazite/xenotime in hydrothermal solutions up to 350(C; 2) determine the stoichiometries and stabilities of REE chloride complexes up to 350(C; and 3) apply our experimental data to problems related to the mobility of REE during water-rock interaction. The data obtained in this study will resolve discrepant theoretical estimates in the literature, provide one of the first experimentally derived sets of thermodynamic data for REE complexes at elevated temperatures, permit quantitative modeling of the role of REE chloride complexes in REE mobility, and serve as a basis for improved theoretical predictions of stability constants for other REE complexes for use until additional experimental data become available. During the course of this project, one graduate and one undergraduate student will be trained in hydrothermal experimental techniques, a number of modern analytical methods, and various aspects of aqueous geochemistry relevant to studies in economic geology and environmental geochemistry. In addition, a new experimental geochemistry laboratory will be set up at Montana Tech.