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

9725287费利这是一项旨在对怀俄明州阿布萨罗卡火山田北部进行地质和地球化学样带调查的提案。由于Absaroka火山岩记录了始新世影响科迪勒拉的最大规模和成分多样化的岩浆事件之一，因此这项研究的结果将极大地提高我们对落基山脉北部第三纪岩浆作用的年龄、成分和岩石成因的认识。这反过来将提供一个基本问题的洞察，即具有潜在的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，并且可能在没有同时代俯冲的情况下形成。分析工作将包括用XRF和ICPMS分析常量和微量元素，用TIMS分析锶、钕和铅的同位素比值，用电子探针进行矿物分析。总体而言，这项研究是从现代岩石学的角度对破译美国西北部新生代地质史的一个悬而未决的问题--即Absaroka岩浆岩的起源--提供现实的第一个方法。

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.