SGER: Reconciling U-series Ages of Major and Accessory Phases

要了解地壳岩浆系统的动力学，就需要了解导致化学变化的过程的类型和这种过程的时间尺度。该奖项将探索一种新的方法来解开为什么使用不同矿物相(辅助相和主相)的U系列同位素组成获得的晶体年龄往往会产生不同的年龄。作为研究计划的一部分，研究人员将在俄勒冈州喀斯喀特南姐妹火山的流纹岩穹顶和新西兰塔拉韦拉火山杂岩的流纹岩穹顶样品中测量一套全面的U系列晶体年龄(即原地锆石238U-230Te年龄和主相和锆石整体分离的226Ra-230Th和238U-230Te年龄)。这一年的探索性研究将使他们能够解决主相和副相结晶之间的时间关系这一核心问题，同时为进一步的工作奠定基础。这一勘探项目的结果可能会立即对该领域产生重大影响，因为它们将为解释不断增长的锆石和主要相年龄数据提供更强有力的背景；了解主要相和辅助相记录相同岩浆事件的程度至关重要，以便从迄今进行的不同系统的研究中总结出岩浆系统是如何工作的。

Understanding the dynamics of crustal magma systems requires knowledge of the types of of processes that lead to chemical changes and the timescales of such processes. This award will explore a novel approach to unravel why crystal ages that are obtained using U-series isotopic compositions of different mineral phases (accessory versus major phases) tend to yield discrepant ages. As part of the research plan, the investigators will measure a comprehensive suite of U-series crystal ages (i.e., in situ 238U-230Th ages in zircon and 226Ra-230Th and 238U-230Th ages in bulk separates of both major phases and zircon) in samples from rhyodacite domes at South Sister Volcano, Oregon Cascades, and rhyolite domes of the Tarawera volcanic complex, New Zealand. This one year of exploratory research will allow them to address the core question of the temporal relationship between major and accessory phase crystallization, while simultaneously laying the foundation for further work. The results of this exploratory project could have immediate and significant impact on the field because they will provide a much stronger context for interpretation of the growing body of age data for zircon and major phases; understanding the extent to which major and accessory phases are recording the same magmatic events is critical in order to make generalizations about how magma systems work from the studies of disparate systems that have been conducted to date.