Collaborative Research: Investigating the Processes and Timescales of Andesite Differentiation: A Comprehensive Petrological and Geochemical Study of Arenal Volcano, Costa Rica

合作研究：调查安山岩分异的过程和时间尺度：哥斯达黎加阿雷纳尔火山的综合岩石学和地球化学研究

• 批准号: 0207316
• 负责人: James Gardner
• 金额: $ 9.41万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-06-01 至 2003-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0207316&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Processes; Timescales

Collaborative Research: Investigating the processes and timescales of andesite differentiation: a comprehensive petrological and geochemical study of Arenal Volcano, Costa RicaEAR-0207185; EAR-0207287; EAR-0207761; EAR-0207316PIs: Gill; Reagan; Tepley; GardnerArenal Volcano in Costa Rica is an excellent natural laboratory in which to test specific hypotheses regarding differentiation mechanisms and the timescales of magmatic processes and their relationship to eruptions. Our objective is to undertake a multi-pronged petrological and geochemical investigation to take advantage of existing data and models. The on-going eruption of Arenal volcano has undergone complex changes in eruptive behavior, and a crucial question is whether those changes relate to different magma storage conditions, such as varying depths and hence initial volatile contents, or to different degassing styles and rates. We will investigate this important issue through several techniques. We seek to determine the timescales of degassing, the residence times and ascent rate of degassed magmas, and the timescales of degassing-induced plagioclase crystallization. We will measure short-lived nuclides within the uranium decay series to constrain the timescales of magmatic processes as well as measure the long-lived isotopic compositions of whole rocks, and mineral separates and individual minerals in the case of Sr, to determine whether there is evidence for involvement of isotopically distinct components during differentiation processes. Lastly, we will measure a suite of major- and trace-element concentrations to evaluate the secular change in Arenal lava composition.The data from these tests will help answer questions such as whether rates of differentiation depend on the depth and degree of crystallization and on the extent and character of degassing; whether crystal and magma residence times can be as short as days to months during near steady-state eruptions of andesite; whether within-eruption changes of magma composition are caused by open-system processes of fractional crystallization plus recharge or assimilation or both; and whether eruption styles are related to degassing history and magma residence time.

合作研究：调查安山岩分化的过程和时间尺度：哥斯达黎加Arenal火山的综合岩石学和地球化学研究EAR-0207185；EAR-0207287；EAR-0207761；EAR-0207316PI：吉尔；里根；特普利；加德纳火山哥斯达黎加的Arenal火山是检验有关分异机制和岩浆过程时间及其与喷发关系的特定假说的优秀自然实验室。我们的目标是进行多管齐下的岩石学和地球化学调查，以利用现有的数据和模型。阿雷纳尔火山的持续喷发经历了喷发行为的复杂变化，一个关键的问题是，这些变化是与不同的岩浆储存条件有关，例如不同的深度和初始挥发分含量，还是与不同的脱气方式和速度有关。我们将通过几种技术来研究这一重要问题。我们试图确定脱气的时间尺度，脱气岩浆的停留时间和上升速率，以及脱气诱导斜长石结晶的时间尺度。我们将测量铀衰变系列中的短寿命核素，以限制岩浆作用的时间尺度，并测量整个岩石、矿物分离和单个矿物的长寿命同位素组成，以确定是否有证据表明在分异过程中涉及不同的同位素成分。最后，我们将测量一套主元素和微量元素浓度来评估古熔岩成分的长期变化。这些测试的数据将有助于回答以下问题：分异速率是否取决于结晶的深度和程度以及脱气的程度和性质；在安山岩的近稳定喷发期间，晶体和岩浆的停留时间是否可以短至数天至数月；岩浆成分的喷发内变化是由分离结晶加再充电或同化的开放系统过程引起的，还是两者兼而有之；喷发方式是否与脱气历史和岩浆停留时间有关。