Magma Evolution and Volcanic Behavior at Cotopaxi, N. Andes

安第斯北部科托帕克西的岩浆演化和火山行为

• 批准号: 9980407
• 负责人: Jon Davidson
• 金额: $ 19.33万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-01-01 至 2002-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9980407&HistoricalAwards=false
• 关键词: Magma; Evolution; Volcanic; Behavior; Cotopaxi

9980407DavidsonCoptopaxi Volcano, Ecuador, provides an unparalleled opportunity to constrain the mechanisms and timescales of magma differentiation at an active arc volcano. A detailed and complete tephra record at the volcano, comprising widespread layers of pumice and ash, has been painstakingly elucidated by our colleagues and collaborators at the Instituto Geofisico in Quito. From this, we can conclude that Cotopaxi has erupted regularly over the past few thousand years, with an average periodicity of around 120 years. The erupted products vary in composition leading to different styles of eruption. The cycles are punctuated by occasional explosive eruptions of rhyolite. The methodology will involve comprehensive petrological and geochemical analyses of the rocks - with a particular emphasis on obtaining information from the constituent phases such as minerals and melt inclusions. By comparing stratigraphically constrained erupted products we will be able to effectively take "snapshots" of the state of the magma reservoir(s) through time and address a number of important questions - including; 1) What are the principle mechanisms of magmatic differentiation (how does a given magma relate to or evolve from one that erupted a hundred years or so earlier)? 2) What are the timescales over which magmatic diversity (how long does it take to generate extreme compositions such as rhyolites)? 3) How do (1) and (2) relate to variations in the volcano's style of eruption?

9980407厄瓜多尔的DavidsonCoptopaxi火山提供了一个无与伦比的机会来限制活动弧火山岩浆分异的机制和时间尺度。基多地球物理研究所的同事和合作者对该火山详细而完整的火山灰记录进行了精心的阐述，其中包括广泛的浮石和火山灰层。由此，我们可以得出结论，科托帕希火山在过去几千年中定期喷发，平均周期约为120年。喷发产物的成分不同，导致不同的喷发风格。这些周期被流纹岩的偶尔爆发性喷发所打断。该方法将涉及对岩石进行全面的岩石学和地球化学分析，特别强调从矿物和熔融包裹体等组成相获得信息。通过比较受地层约束的喷发产物，我们将能够有效地拍摄岩浆储层随时间推移的状态“快照”，并解决一些重要问题--包括：1）岩浆分异的主要机制是什么（给定的岩浆如何与一百年前喷发的岩浆相关或从其演变而来）？2)岩浆多样性的时间尺度是什么（产生极端的成分如韵律需要多长时间）？ 3)（1）和（2）与火山喷发方式的变化有什么关系？