Evolution of LREE+Th Distributions in Minerals During Prograde Metamorphism

独居石是变质岩中常见的微量矿物，对年龄测定具有重要意义。轻稀土元素(LREE)是独居石的主要化学成分，但在独居石在岩石中形成之前，轻稀土元素的宿主尚不清楚。利用大烟山国家公园的天然样品，这项工作将区分LREE是由主要的硅酸盐矿物赋存的，还是由尿囊石等富含LREE的微量矿物赋存的。这项研究还将显示独居石是瞬间形成的，还是具有长期的生长历史。这些结果将有助于表征独居石的形成反应，以提高我们对独居石提供的年龄的理解，并更好地约束产生Smokies和其他山脉带的构造过程。研究结果还将用于改善每年参观大烟山国家公园的1000万游客的讲解辅助工具。

Monazite is a common trace mineral in metamorphic rocks, and is critical for age determinations. The Light Rare-Earth Elements (LREEs) are a main chemical constituent of monazite, yet the host of LREEs before monazite forms in a rock is unclear. Using natural samples from Great Smoky Mountains National Park, this work will discriminate whether LREEs are hosted by major silicate minerals or LREE-rich trace minerals such as allanite. The work will also show whether monazite forms instantaneously or has a protracted growth history. These results will help characterize monazite-forming reactions to improve our understanding of the ages monazite provide, and better constrain the tectonic processes that produced the Smokies and other mountain belts. Results will also be used to improve interpretive aids for the 10 million people that visit the Great Smoky Mountains National Park each year.