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.

智力优点。该提案旨在提高对镁铁质中混合（H2O + CO2）岩浆挥发物的溶解度关系的理解，该岩石在广泛的组成范围内与ARC相关的熔岩。最近的工作表明，镁铁质弧熔岩中发现的组成可变性可能会导致溶解度行为发生重大变化，而这些行为在当前模型中的解释很差。缺乏对这种基本化学行为的限制严重阻碍了在弧形环境中涉及挥发物的观察工作的解释，尤其是熔体纳入测量值的观察工作。这直接影响我们了解关键基本过程的能力，例如岩浆波动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性地与各种H2ocos的含量融合型型H2oco2的含量，以解决这一重要需求，以解决这一重要需求。喷发前岩浆条件。该实验将在活塞缸设备中使用新技术进行，该技术可以准确地达到亚电导压力（200-500 MPa），同时保持设备的快速脉冲优势。在100 MPa的支持实验也将在内部加热压力容器的快速脉动中进行。在每个实验中，流体相的H2O/CO2比率将通过真空测量法精确测量，并使用高温测量，FTIR光谱和模拟器测量的熔体中溶解的H2O和CO2。因此，收集的数据将用于开发经验模型，以在一系列玄武岩组成的范围内准确计算混合挥发性饱和度。理解挥发物在Mafic Arc Magmas中的行为和演变是解释俯冲式岩岩岩浆岩岩的岩石学和火山学遵守的关键部分。只有通过结合对给定岩浆组成的挥发性溶解度行为的精确估计的结合测量，才能实现这种理解。拟议的工作代表了生成所需的关键实验数据的重要一步，以解释其他工人目前正在衡量的混合挥发性内容，这是在广泛的镁铁质，与弧相关的岩浆的广泛组成范围内测量的。这项工作将在培训毕业生和本科生以及许多国际合作者和独立研究人员的高压热量技术方面非常成功的实验性岩石学实验室。该具体建议包括对两个女性大学生的支持，并将帮助实验室继续开发新颖的实验方法和实验性岩石学应用程序。我们还预期了大量的经过漫画分析的玻璃，这将有助于比较次级挥发性测量技术，例如SIMS和FTIR。