Geochemistry and Petrogenesis of Eocene Potassic Volcanism in the Absaroka Volcanic Field, Wyoming

这是一项旨在对怀俄明州Absaroka火山区北部进行地质和地球化学样带的提案。由于Absaroka火山岩记录了始新世影响科迪勒拉的最大量和成分最多样化的岩浆事件之一，因此本研究的结果将大大提高我们对落基山脉北部第三纪岩浆活动的年龄、成分和岩石成因的认识。反过来，这将提供对具有潜在弧形钙碱性亲和力和跨走向地球化学趋势的岩套如何在如此不同的构造环境中形成的基本问题的见解，并且可能在没有同时期俯冲作用的情况下形成。分析工作将包括用XRF和ICP-MS分析主要元素和微量元素，用TIMS分析Sr、Nd和Pb同位素比率，以及用电子探针分析矿物。总的来说，这项研究代表了一个现实的第一个方法，为破译美国西北部新生代地质历史的一个悬而未决的问题提供了一个现代岩石学的观点：即Absaroka岩浆岩的起源。

9725287 Feeley This is a proposal designed to carry out a geological and geochemical transect across the northern part of the Absaroka volcanic field, Wyoming. Because the Absaroka volcanic rocks record one of the most voluminous and compositionally diverse magmatic episodes to affect the Cordillera during the Eocene, the results obtained from this study will significantly improve our knowledge of the ages, compositions, and petrogenesis of Tertiary magmatism in the northern Rocky Mountains. This, in turn, will provide insight into the fundamental problem of how rock suites with potentially arc-like calc-alkaline affinities and across-strike geochemical trends can form in such different tectonic environments, and possibly in the absence of contemporaneous subduction. The analytical work will include analysis of major and trace elements by XRF and ICP-MS, analysis of Sr, Nd, and Pb isotopic ratios by TIMS, and mineral analysis by electron microprobe. Overall, this study represents a realistic first approach towards providing a modern petrologic perspective on one of the outstanding unresolved issues in deciphering the Cenozoic geological history of the northwestern United States: namely, the origin of the Absaroka magmatic rocks.