Distribution and Origin of Gas and Volatiles in the Bishop Magma

主教岩浆中气体和挥发物的分布和来源

• 批准号: 8904070
• 负责人: Alfred Anderson
• 金额: $ 10万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-07-01 至 1992-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8904070&HistoricalAwards=false
• 关键词: Distribution; Origin; Gas; Volatiles; Bishop

Inclusions of glass in volcanic phenocrysts can reveal the preeruptive state of magma and its pressure of crystallization. Such knowledge is needed to understand volcanic eruptions and the formation and evolution of magmas and ores. This project will determine the vesicularity and crystal content of individual lumps of pumice as well as the compositions of phenocrysts and concentrations of H2O and CO2 in glassy and revitrified inclusions in quartz and feldspar phenocrysts from stratigraphically controlled sites in the rhyolitic Bishop Tuff, Calif. These determinations will be used to assess the following postulates: 1) An accumulation of gas existed in the upper part of the preerupted body of magma; 2) Gas accumulation was mostly responsible for a strong upward decrease in bulk magma density and consequent prevention of convection and survival of magmatic zoning during eruption; 3) the transition from plinian to ash- flow style of eruption corresponds to a sharp change in the amount of accumulated gas; 4) gas accumulation largely derived from deeper levels of differentiation rather than in situ crystallization; 5) H2O was added to magma during ascent.

火山斑晶中的玻璃包裹体可以揭示 岩浆喷发前的状态及其结晶压力。 这些知识是了解火山爆发和 岩浆和矿石的形成和演化。 该项目将 测定个体的囊泡度和晶体含量 浮石块以及斑晶的组合物， 水和CO2浓度的玻璃和再生 石英和长石斑晶中的包裹体 流纹质主教凝灰岩中的地层控制点， 加州 这些测定结果将用于评估以下内容 认为：1）上部存在天然气聚集 2）天然气成藏主要是以岩浆活动为主; 导致了岩浆体积密度的强烈上升 从而阻止对流和岩浆的存活 火山喷发时的分带; 3）从碎屑岩到火山灰的过渡。 喷发的流动方式对应于火山喷发的急剧变化， 4）天然气成藏主要来源于 从更深层次的分化，而不是在原位 （5）岩浆上升过程中加入了H_2O。