Zr-Mineral Aqueous Solubilities and Zircon/(Fluid-Melt) Partitioning

矿物锆石（ZrSiO 4）通常用于确定地质过程的日期，斜锆石（ZrO 2）正在成为一种越来越重要的地质年代学工具。 虽然锆被认为是不动的，锆石非常稳定和耐用，许多最近的实地研究已经确定了锆石的水热蚀变或沉淀的热液流体。 将进行2 kbar下的双胶囊冷密封压力容器实验，以1）确定锆矿物锆石和斜锆石在含水流体中可溶的条件，以及2）表征微量元素（包括Th和U）在锆石、含水流体和花岗岩熔体之间的分配。 锆流体溶解度和分配实验将在450- 750 ℃和可变的流体pH值和氧逸度（fO 2）进行，而一组平行的锆熔体分配实验将在750 ℃和变量fO 2进行。 岩浆和热液锆石独特的微量元素特征的识别将允许准确解释锆石年龄。 例如，微量元素浓度可用于将锆石识别为热液，溶解度系统学可用于限制其形成的条件，使得测量的年龄可被解释为在特定条件（温度、流体pH、fO 2）下流体渗透的时间。 除了帮助解释热液锆石及其测得的年龄外，溶解度系统学还可用于评估锆石和斜锆石储存钚的可行性。 本项目将资助一位现任硕士的论文研究。学生，2-3个未来的M.S.或博士学生，2-3名本科生。 购买的设备将供本研究项目和其他研究项目的大量研究人员使用。 该补助金还将帮助开发一个新的跨学科环境科学博士学位。该项目与范德比尔特的土木与环境工程系合作。

The mineral zircon (ZrSiO4) is commonly used to date geological processes, and baddeleyite (ZrO2) is becoming an increasingly important geochronological tool. Although Zr is considered to be immobile and zircon extremely stable and durable, many recent field studies have identified zircon that was hydrothermally altered or precipitated from hydrothermal fluids. Double-capsule cold seal pressure vessel experiments at 2 kbar will be conducted to 1) identify the conditions under which the zirconium-minerals zircon and baddeleyite are soluble in aqueous fluids, and 2) characterize the partitioning of trace elements including Th and U between zircon, aqueous fluids and granitic melts. Zircon-fluid solubility and partitioning experiments will be conducted at 450-750C and variable fluid pH and oxygen fugacity (fO2), while a parallel set of zircon-melt partitioning experiments will be conducted at 750C and variable fO2. Identification of unique trace element signatures of magmatic and hydrothermal zircons will allow for accurate interpretation of zircon ages. For example, trace element concentrations can be used to identify a zircon as hydrothermal, and solubility systematics can be used to constrain the conditions under which it formed, so that the measured age can be interpreted to date the time of fluid infiltration under specific conditions (temperature, fluid pH, fO2). In addition to aiding interpretation of hydrothermal zircons and their measured ages, the solubility systematics can be used to assess the viability of zircon and baddeleyite for storage of plutonium. This project will fund the thesis research of one current M.S. student, 2-3 future M.S. or Ph.D. students, and 2-3 undergraduate students. Equipment purchased will be used by a large number of investigators in this and other research projects. The grant will also aid in the development of a new interdisciplinary Environmental Science Ph.D. program in collaboration with the Department of Civil and Environmental Engineering at Vanderbilt.