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

Rutherford-0073771该提案涉及三个项目，都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是如何发生的。 这些任务涉及一系列分析工作（即，电子微探针，离子探针，F.T.I.R光谱）在现场研究过程中收集的样品，并在控制的P，T和fO 2条件下实验制备的样品。 第一个项目是对1912年火山爆发的调查。卡特迈火山在一次喷发中爆发了三种成分不同的岩浆。 该研究同时也是对岩浆混合过程的一次探索，同时也是对Hildreth提出的岩浆分带储存区假说的一次检验。 第二项任务是获得火山气体成分作为P、T、fO 2的函数以及共存晶体和熔体成分的基本数据。 本研究将考虑CO2-H2O-S组成气相。 第三个项目是研究加州的黑丘和邻近的沙斯塔山几乎同时发生的火山爆发。 这项工作的目的是确定两次喷发前的岩浆条件，并制定一个表达式有关的岩浆条件和共存的斜长石和角闪石的组成，这是突出的阶段，在这些喷发。

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.