Understanding the Volatile Evolution of Arc Magmas: Alkalies and Mixed (H2O + CO2) Volatile Solubility in Basalts and Basaltic Andesites

了解弧岩浆的挥发性演化：玄武岩和玄武安山岩中的碱金属和混合 (H2O CO2) 挥发性溶解度

• 批准号: 0838563
• 负责人: Gordon Moore
• 金额: $ 20.47万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-01-15 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838563&HistoricalAwards=false
• 关键词: Understanding; Volatile; Evolution; Arc; Magmas

Intellectual merit. This proposal aims to improve understanding of the solubility relationships of mixed (H2O + CO2) magmatic volatiles in mafic, arc-related lavas over a broad composition range. Recent work has shown that the compositional variability found in mafic arc lavas can lead to significant changes in solubility behavior that are poorly accounted for in current models. The lack of constraints on such fundamental chemical behavior severely hampers the interpretations of observational work involving volatiles in arc settings, particularly that of melt inclusion measurements. This directly affects our ability to understand critically fundamental processes such as the influence of magmatic volatile contents on magma chemistry and eruption/degassing dynamics, or the role of arc volcanic processes in global H2O and CO2 budgets.The proposed work will address this important need via experimentally saturating mafic melts of strategically chosen compositions with various H2OCO2 fluids at pressures and temperatures relevant to pre-eruptive magmatic conditions. The experiments will be conducted in a piston cylinder apparatus using new techniques that accurately achieve sub-volcanic pressures (200-500 MPa), while maintaining the rapid-quench advantage of the device. Supporting experiments at 100 MPa will also be conducted in a rapid-quench internally heated pressure vessel. In each experiment, the H2O/CO2 ratio of the fluid phase will be precisely measured by vacuum manometry, and the dissolved H2O andCO2 in the melt measured using high temperature manometry, FTIR spectroscopy, as well as SIMS. The data thereby gathered will be used to develop an empirical model to accurately calculate mixed volatile saturation over a range of basaltic compositions.Understanding the behavior and evolution of volatiles in mafic arc magmas is a key part of interpreting petrologic and volcanologic observations of subduction-zone magmatism. This understanding can only achieved by combined measurements of pre-eruptive magmatic volatile content and precise estimates of the volatile solubility behavior of a given magma composition. The proposed work represents a significant step towards generating critical experimental data needed to interpret the mixed volatile contents currently being measured by other workers over a broad compositional range of mafic, arc-related magmas.Broader impacts. The experimental petrology laboratory where this work will be conducted has been very successful in training graduates and undergraduates, as well as many international collaborators and independent researchers, in high pressure-temperature techniques. This specific proposal includes support for two female undergraduates, and will help the lab to continue to develop novel experimental approaches and applications to experimental petrology. We also anticipate the large number of manometrically analyzed glasses that will result to be useful for comparison of secondary volatile measurement techniques such as SIMS and FTIR.

智力上的优点。这一建议的目的是提高认识的溶解度关系的混合（H2O + CO2）岩浆挥发分在基性岩，弧有关的熔岩在一个广泛的组成范围。最近的研究表明，在镁铁质弧熔岩中发现的成分变化可以导致溶解度行为的显着变化，在目前的模型中解释得很差。这种基本的化学行为缺乏约束，严重阻碍了解释的观察工作，涉及挥发分在电弧设置，特别是熔体包裹体测量。这直接影响到我们理解关键的基本过程的能力，例如岩浆挥发物含量对岩浆化学和喷发/脱气动力学的影响，或弧火山过程在全球H2O和CO2预算中的作用。拟议的工作将通过实验饱和战略选择组成的镁铁质熔体与各种H2OCO 2流体在压力和温度相关的前，岩浆喷发条件实验将在活塞缸装置中进行，使用新技术，准确地实现亚火山压力（200-500 MPa），同时保持该设备的快速淬火优势。还将在快速淬火内部加热压力容器中进行100 MPa的辅助实验。在每个实验中，流体相的H2O/CO2比率将通过真空压力计精确测量，并且熔体中溶解的H2O和CO2使用高温压力计、FTIR光谱以及西姆斯测量。由此收集的数据将被用来开发一个经验模型，以准确地计算混合挥发分饱和度范围内的玄武岩compositions.Understanding基性岩弧岩浆中的挥发分的行为和演变是解释俯冲带岩浆活动的岩石学和火山学观测的关键部分。这种理解只能通过结合测量喷发前岩浆的挥发分含量和精确估计给定岩浆成分的挥发分溶解度行为来实现。拟议的工作是一个重要的一步，产生关键的实验数据，需要解释目前正在测量的混合挥发性成分的其他工人在广泛的组成范围内的镁铁质，弧相关的岩浆。进行这项工作的实验岩石学实验室在培训研究生和本科生以及许多国际合作者和独立研究人员方面非常成功。这项具体的建议包括支持两名女大学生，并将帮助实验室继续开发新的实验方法和应用实验岩石学。我们还预计大量的测压分析的玻璃，将导致是有用的二次挥发性测量技术，如西姆斯和FTIR的比较。