Evolution of LREE+Th Distributions in Minerals During Prograde Metamorphism

独居石是变质岩中常见的微量元素矿物，是确定岩石年龄的重要指标。轻稀土元素是独居石的主要化学成分，但独居石形成前轻稀土元素的主体尚不清楚。利用大烟山国家公园的天然样品，这项工作将区分轻稀土元素是否由主要的硅酸盐矿物或富含轻稀土元素的微量矿物，如褐帘石。这项工作还将显示独居石是瞬间形成的，还是有一个漫长的生长历史。这些结果将有助于描述独居石形成反应，以提高我们对独居石提供的年龄的理解，并更好地约束产生大烟山和其他山脉带的构造过程。研究结果还将用于改善每年访问大烟山国家公园的1000万人的解说辅助工具。

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.