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：哥斯达黎加阿纳尔火山的综合岩石学和地球化学研究哥斯达黎加的GardnerArenal火山是一个极好的天然实验室，可以测试关于分化机制和时间尺度的特定假设。岩浆过程及其与火山爆发的关系。我们的目标是进行多方面的岩石学和地球化学调查，以利用现有的数据和模型。持续喷发的阿纳尔火山经历了复杂的喷发行为的变化，一个关键的问题是，这些变化是否与不同的岩浆储存条件，如不同的深度，从而初始挥发分含量，或不同的脱气风格和速率。我们将通过几种技术来研究这个重要问题。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，以限制岩浆过程的时间尺度，以及测量整个岩石的长寿命同位素组成，矿物分离和单个矿物的情况下，Sr，以确定是否有证据参与同位素不同的成分在分化过程中。最后，我们将测量一组主要和微量元素的浓度，以评估阿纳尔熔岩成分的长期变化，这些测试的数据将有助于回答一些问题，如分异率是否取决于结晶的深度和程度，以及脱气的程度和性质;在安山岩近稳态喷发期间，晶体和岩浆的停留时间是否可以短至几天到几个月;喷发内岩浆成分的变化是否是由分离结晶加补给或同化或两者兼而有之的开放系统过程引起的，以及喷发样式是否与脱气历史和岩浆停留时间有关。

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.