Petrogenesis of the Mt. Jefferson Area, Oregon High Cascades

最近的制图和大量化学分析已经确定，在俄勒冈州高喀斯喀特山脉的杰斐逊山地区存在一个长期存在的安山岩和英安质火山活动区。该项目旨在通过精确的K-Ar年龄测定进一步限制该火山场的时间演化，并通过稀土元素（REE）和同位素（O， Sr和Nd）分析更好地了解该火山场的岩石成因。杰佛逊山周围的火山场在5年的时间里进行了详细的测绘，并建立了一个涉及150多个地图单元的广泛而详细的地层格架，因此特别适合进行这项研究。在任何地方，很少有弧的部分被如此详细地了解。在杰佛逊山地区的岩石中也获得了广泛的大块成分和电子探针数据库。这些数据证明了这些岩石中开放系统过程（可能是岩浆混合）的重要性。这个结论适用于所有被检查的岩石类型，包括玄武岩安山岩、安山岩和岩屑岩。

Recent mapping and bulk chemical analyses have established the existence of a long-lived field of andesitic and dacitic volcanism in the Mt. Jefferson area of the High Cascade Range in Oregon. The project aims to further constrain the temporal evolution of this volcanic field with precise K-Ar age dating, and to better understand the petrogenesis of the filed with rare earth element (REE) and isotopic (O, Sr, and Nd) analyses. The volcanic field around Mt. Jefferson is particularly suitable for this study as it has been mapped in detail over a period of five years, and an extensive and detailed stratigraphic framework involving some 150 map units has been established. Few parts of arcs anywhere are known in such detail. An extensive bulk composition and electron microprobe data base has also been acquired on the Mt. Jefferson area rocks. These data demonstrate the importance of open system processes, presumably magma mixing, in these rocks. this conclusion applies to all rock types examined, including basaltic andesites, andesites, and dactites.