Measurement of the Solubilities of Scheelite and Ferberite in Hydrothermal Solutions With In-Situ pH Measurement

钨是一种具有重要战略意义的金属。通常没有可靠的热力学数据来计算最重要的钨矿石白钨矿(CaWO4)和铁钨矿(FeWO4)的溶解度，以及钨在热液中的传质。然而，这些数据是开发热液钨矿床综合成因模型所必需的，这些模型可以指导新钨资源的勘探。因此，建议进行一项研究，在饱和水蒸气压力下测量白钨矿和阿魏酸矿在非络合溶液中的溶解度，作为温度从50摄氏度到290摄氏度、pH和离子强度的函数。酸碱度将使用在橡树岭国家实验室开发并成功使用的氢电极浓度计(HECC)直接在现场监测。根据测得的溶解度随pH和离子强度的变化，可以求出白钨矿和亚铁铅矿的溶解度积，以及钨酸(H_2WO_40)的离解常数，这些都是计算钨传质的基本热力学数据。该项目将涉及一名博士生，他将接受热液地球化学和高压/高温实验方法方面的培训。该项目不仅将获得高质量的热力学数据，用来计算钨矿物在热液中的溶解度和W的传质，而且还将为PI提供一个HECC，用于未来对其他感兴趣的地球化学系统的研究。

WoodEAR-0087065Tungsten is a metal of strategic importance. Reliable thermodynamic data with which to calculate the solubilities of the most important tungsten ores, scheelite (CaWO4) and ferberite (FeWO4), and the mass transfer of tungsten, in hydrothermal solutions are generally not available. Yet, such data are required to develop comprehensive genetic models of hydrothermal tungsten deposits; these models can guide exploration for new tungsten resources. A study is therefore proposed in which the solubilities of scheelite and ferberite will be measured in non-complexing solutions at saturated water vapor pressure as a function of temperature from 50 degrees to 290 degrees C, pH and ionic strength. The pH will be monitored directly in-situ using a hydrogen electrode concentration cell (HECC) of the type developed and used successfully at Oak Ridge National Laboratory. From the solubilities measured as a function of pH and ionic strength, the solubility products for scheelite and ferberite, and the dissociation constants for tungstic acid (H2WO40), all of which are essential thermodynamic data for the calculation of W mass transfer, can be derived. The project will involve one Ph.D. student who will be trained in hydrothermal geochemistry and high-pressure/high-temperature experimental methods. This project will not only result in the acquisition of high-quality thermodynamic data with which to calculate tungsten mineral solubilities and W mass transfer in hydrothermal solutions, but will also provide the PI with an HECC for future studies of other systems of geochemical interest.