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

9705661木材知识的行为稀土元素（REE）在高温水溶液中是必需的，在以下领域：1）地质年代学（即，岩石测年）; 2）稀土矿存款地质学; 3）核废料的补救和安全储存。遗憾的是，缺乏更好地了解稀土元素地球化学所需的相关数据。预计在许多天然溶液中，REE将与氯离子形成溶解络合物，并且已知REE磷酸盐相（独居石、磷钇矿、杆闪石）是常见的REE矿物。因此，本建议的目标是：1）确定独居石/磷钇矿在热液溶液中的溶解度高达350（C）; 2）确定化学计量和稳定性的稀土氯化物络合物高达350（C）;和3）应用我们的实验数据的流动性的稀土元素在水-岩石相互作用的问题。在这项研究中获得的数据将解决不一致的理论估计在文献中，提供了第一个实验得出的一套在高温下的REE络合物的热力学数据，允许定量建模的作用，稀土氯化物络合物在REE的流动性，并作为一个基础，用于其他稀土络合物的稳定常数的改进的理论预测，直到更多的实验数据变得可用。在本项目期间，将对一名研究生和一名本科生进行热液实验技术、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地球化学各方面的培训。此外，蒙大拿理工学院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.