Laboratory and Field Investigations of Monazite Paragenesis, Growth Kinetics, Textural Development, and U-Th-Pb Chronometry in Igneous and High-Grade Metamorphic Rocks

9873626艾尔斯独居石颗粒在火成岩和高级变质岩中通常包含多个生长带，产生对应于岩石历史中多个事件的U，Th-Pb年龄。 所提出的实验室和现场实验旨在表征独居石生长和重结晶。 从具有良好特征历史的地区（内华达州南部的一个岩体，北卡罗来纳州和加州的变质岩）收集的天然独居石中，对生长带的结构特征、年龄和成分进行原位测量，将有助于确定独居石生长的时间和条件。 在类似条件下进行的实验室实验将量化生长机制和速率，并证实天然独居石分区的结构解释。 由于生长和重结晶往往与流体的流入有关，对含有独居石和流体的岩石进行实验将有助于确定热液生长和重结晶的特征结构特征，包括晶体粒度分布、分区模式、包裹体/宿主关系和润湿角。 这些功能对流体成分，主机晶粒尺寸和粗化率，以及温度的依赖关系也将被调查，以确定天然独居石的生长条件。 结果将细化天然独居石的结构和分带的解释和测量的U，Th-Pb独居石年龄与特定的地球化学和构造事件的相关性。

9873626AyersMonazite grains in igneous and high-grade metamorphic rocks often contain multiple growth zones that yield U,Th-Pb dates corresponding to multiple events in the history of a rock. The proposed lab and field experiments are designed to characterize monazite growth and recrystallization. In-situ measurements of textural features, ages, and compositions of growth zones in natural monazites collected from regions with well-characterized histories (a pluton in southern Nevada, metamorphic terranes in North Carolina and California) will help to establish the timing and conditions of monazite growth. Lab experiments conducted undersimilar conditions will quantify growth mechanisms and rates and corroborate textural interpretations of zoning in natural monazites. Because growth and recrystallization often appears to be related to fluid influx, experiments on rocks containing monazite and fluid will help to identify characteristic textural features of hydrothermal growth and recrystallization including crystal size distributions, zoning patterns, inclusion/host relations, and wetting angles. The dependence of these features on fluid composition, host grain size and coarsening rate, and temperature will also be investigated to identify conditions of growth of natural monazites. Results will refine interpretations of texture and zoning in natural monazites and the correlation of measured U,Th-Pb monazite ages with specific geochemical and tectonic events.