CAREER: Stable Isotope (18O/16O and D/H) Studies of Continental Arc Magmatism

Feeley 9983769稳定同位素比值可以对火成岩的岩浆源和挥发源的起源及其演化的分异过程提供重要的制约。 然而，传统的玻璃质火山岩的全岩同位素测量可能无法反映岩浆的价值，因为在喷发和喷发后的脱气和蚀变过程中的修改。 相比之下，斑晶分析提供了一个准确和精确的手段，确定同位素变化所造成的岩浆过程。 这项职业研究将检查稳定同位素组成（18 O/16 O和D/H）的斑晶从俯冲相关的火山岩的变化，强调（但不限于）中间熔岩，提供有关岩石质量平衡和浅地壳脱气过程在钙碱性成层火山的信息。 拟议的研究计划包括两个部分：（1）详细研究拉森火山中心在个别喷发周期和该中心长期岩浆历史中喷发的岩浆产物的氧同位素变化;（2）研究拉森和圣海伦火山岩石中含水斑晶的氢同位素组成。 教育计划包括三个层次的教学：1）新课程开发; 2）传统的研究生培养; 3）专业本科生研究培训。 创建的新课程将是一个低年级的服务学习课程，重点是蒙大拿州西南部的火山灾害，以及同位素地球化学的高年级课程。 本科培训计划的目的是为有才华的学生，特别是那些计划从事研究型职业的学生，提供现场，实验室和传播技能的一对一培训。

Feeley9983769Stable isotope ratios can provide important constraints on the origins of the magmatic and volatile sources of igneous rocks and the differentiation processes by which they evolve. However, traditional whole-rock isotopic measurements of glassy volcanic rocks may not reflect magmatic values because of modification during eruptive and post-eruptive degassing and alteration. In contrast, analyses of phenocrysts provides an accurate and precise means of determining isotopic variations resulting from magmatic processes. This Career research will examine variations in stable isotope compositions (18O/16O and D/H) of phenocrysts from subduction-related volcanic rocks, emphasizing (but not restricted to) intermediate lavas that provide information on the petrologic mass balance and shallow crustal degassing processes at calc-alkaline stratovolcanoes. The proposed Research Plan involves two parts: (1) detailed study of oxygen isotope variations for magmatic products erupted at the Lassen volcanic center during individual eruptive cycles and over the prolonged magmatic history of the center and (2) study of hydrogen isotope compositions of hydrous phenocrysts in rocks from Lassen and Mount St. Helens. The Education Plan involves three levels of instruction: 1) new course development; 2) traditional graduate student training, and 3) specialized undergraduate research training. The new courses created will be a lower-division, service-learning course focusing on volcanic hazards in southwest Montana, and an upper-division course in isotope geochemistry. The purpose of the undergraduate training program is to provide talented students, especially those planning on a research-oriented career, with one-on-one training in field, laboratory, and dissemination skills.