Collaborative Research: Volatiles in Aleutian Arc Magmas

该项目旨在确定阿拉斯加阿留申群岛活火山喷发前岩浆中溶解的水和二氧化碳的数量。水对这些岩浆的各个方面都至关重要，从火山下面的管道系统，到它们在俯冲带的起源，再到它们为火山喷发提供燃料的气体含量。尽管水具有首要的重要性，但只在有限的火山样本中确定了水。阿拉斯加的阿留申火山提供了将水含量与俯冲带现有的地球化学示踪剂、板块俯冲的地球物理参数以及岩浆储存深度和火山变形的大地测量相关联的绝佳机会。后一种联系将通过安装在奥古斯丁和阿库坦火山上的板块边界观测站作为地球观测设备的一部分而成为可能。该项目是在一项为期一年的试点研究的基础上进行的，该研究是为收集适当的样本而资助的。研究人员从阿留申群岛的10座火山中收集了大约100个样本，并计划从西古安火山收集更多样本。初步数据显示，奥古斯丁火山（Augustine volcano）的基性弧熔体包裹体（7 wt%）含水量是世界上最高的。奥古斯丁火山目前正在喷发。目前项目的主要活动是通过华盛顿卡内基研究所的离子探针分析困在石晶体中的熔体包裹体的挥发性含量（H2O, CO2， S, Cl,），以及波士顿大学的激光烧蚀电感耦合等离子体质谱分析微量元素（包括La， Ba, Sr， U, Th, Pb, Nb）。另一个重点将是开发估算斜辉石晶体岩浆含水量的新技术，一种是基于它们的稀土元素模式，另一种是基于它们的水含量。该项目将帮助一名女研究生完成她的博士学位，并将支持波士顿大学的本科生研究。

This project aims to determine the amount of water and carbon dioxide dissolved in magma before it erupts from active volcanoes in the Aleutian islands, Alaska. Water in particular is critical to every aspect of these magmas, from their plumbing system beneath the volcanoes, to their very origin in the subduction zone, to their gas content which fuels eruptions. Despite its primary importance, water has been determined in only a limited number of volcanic samples. The Aleutian volcanoes of Alaska offer a prime opportunity to relate water contents to existing geochemical tracers from the subduction zone, geophysical parameters of plate subduction, and geodetic measurement of magma storage depths and volcano deformation. The latter linkage will be possible through Plate Boundary Observatory installations on Augustine and Akutan volcanoes as part of the EarthScope facility.This project follows from a one-year pilot study funded to collect appropriate samples. The researchers have ~ 100 tephra samples from 10 Aleutian volcanoes, and plan to collect more from Seguam volcano. Preliminary data are promising, showing among the highest water contents measured in the world in mafic arc melt inclusions ( 7 wt%) from Augustine volcano, which is currently erupting. The primary activity of the current project is to analyze melt inclusions trapped in olivine crystals for their volatile content (H2O, CO2, S, Cl,) by ion microprobe at the Carnegie Institution of Washington, and trace elements (including La, Ba, Sr, U, Th, Pb, Nb) by laser-ablation inductively coupled plasma mass spectrometry at Boston University. Another major focus will be the development of new techniques for estimating the water content of magmas from clinopyroxene crystals, one based on their rare earth element pattern, and the other on their H2O content. This project will enable a female graduate student to complete her PhD work, and will support undergraduate research at Boston University.