Volcanic Processes in Subduction Zone Magmas: Composition, Abundance, and Role of C-O-H-S Volatiles

这项建议涉及三个项目，旨在更全面地了解富含气体的俯冲带火山系统中岩浆混合、结晶、晶体-熔体分离和脱气等岩浆过程。这些任务涉及对实地研究期间收集的样品以及在受控P、T和fO2条件下实验制备的样品进行的一系列分析工作(即电子微探针、离子探针、FTIR光谱分析)。第一个项目是对1912年火山喷发的调查。在卡特迈，三个成分截然不同的岩浆在一个事件中喷发。这项研究既是对岩浆混合过程的调查，也是对希尔德雷思提出的带状岩浆储存区假说的检验。第二项任务是获得关于火山气体的组成随P、T、fO2的函数以及共存的晶体和熔体的组成的基本数据。本研究将考虑CO_2-H_2O-S组成气相。第三个项目是对几乎同时发生在加利福尼亚州黑巴特和邻近的沙斯塔火山的火山喷发进行研究。这项工作的目的是确定两次喷发的喷发前岩浆条件，并建立一个与岩浆条件和共存的斜长石和角闪石的成分之间的关系的表达式，这两次喷发中的突出物相。

RutherfordEAR-0073771This proposal involves three projects, all directed at developing a more complete understanding of how the magmatic processes such as magma mixing, crystallization, crystal-melt separation, and degassing occur in gas-rich, subduction zone volcanic systems. The tasks involve a range of analytical work (i.e., electron microprobe, ion-probe, F.T.I.R spectroscopy) on samples collected during field study, and on samples prepared experimentally under controlled P, T, and fO2, conditions. The first project is an investigation of the 1912 eruption of Mt. Katmai where three compositionally distinct magmas were erupted in a single event. The study is simultaneously an investigation of magma mixing processes, and a test of the zoned magma storage region hypothesis proposed by Hildreth. The second task is one in which fundamental data will be obtained on the composition of volcanic gases as a function of P, T, fO2, and the composition of coexisting crystals and melt. This study will consider CO2-H2O-S composition gas phases. The third project is a study of the volcanic eruptions which occurred almost simultaneously at Black Butte and adjacent Mount Shasta in California. The objective of this work is to determine the pre-eruption magma condition for the two eruptions, and to develop an expression relating magmatic conditions and the compositions of coexisting plagioclase and hornblende which are prominent phases in these eruptions.