Implications of variable initial water content for mobilising magmatic metals in arc volcanoes

可变初始水含量对弧火山中岩浆金属流动的影响

• 批准号: 2698388
• 金额: --
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2698388
• 关键词: Implications; variable; initial; water; content

The migration and sequestration of metallic elements within magmatic systems modulates the environmental impacts of volcanic emissions and the development of ore deposits (Edmonds et al., 2022 Tattitch et al., 2021). Many elements classified as "environmental pollutants" by public health agencies are volatile in silicate melts (Ilyinskaya et al., 2021). Volcanoes in different tectonic settings emit contrasting trace metal "fingerprints", which are linked to differences in the relative timings of vapour and sulfide saturation (Edmonds et al., 2018). Arc volcanoes erupt magmas containing a wide range of primary water contents, spanning less than 1 wt% to more than 7 wt% H2O, inherited from heterogeneities in mantle source and subduction contributions (Plank et al., 2013 Ruscitto et al., 2012). Magmatic water content influences the physical and chemical properties of silicate melts (e.g., viscosity and crystallisation dynamics) and is consequently a key control on the timing/pressure of vapour saturation - and therefore availability of a hydrous fluid phase for trace elements to partition into according to their melt-fluid partition coefficients - and the conditions under which magmas are stored in the crust (Edmonds et al., 2022). However, the role of primary water content on metal partitioning has yet to be investigated systematically.This project identifies two arc volcanoes-Fuego and Pacaya, Guatemala-with low andhigh magmatic water contents, respectively (Lloyd et al., 2014 Walker et al., 2003). Theoverarching aim is to reconstruct and compare the evolution of their trace metal cargoes using established petrological strategies. Targeting Fuego and Pacaya for end-member comparisons of magmatic water content avoids introducing additional uncertainties that may influence metal behaviour such as along-arc or inter-arc variations in slab flux or crustal thickness. This research will involve field sampling of erupted rocks and emitted metal aerosols in the gas plume. Laboratory work will focus on petrological analysis of melt inclusions and glasses, including ion probe analyses of volatile contents, together with geochemical analysis of plume aerosol samples collected on filters. Petrological and thermodynamic modelling will provide a framework to interpret our geochemical data and, in particular, to relate metal behaviour to crystallisation processes and the composition of the exsolved volatile phase in silicate melts. This project will also explore the potential for developing non-traditional approaches to assess the environmental impact of volcanic emissions: in particular, the feasibility of using trace metals in vegetation, soil, and hydrological samples to assess the delivery mechanisms and pathways of volcanogenic trace metal pollutants to the environment, with consequent implications for ecological science and hazard assessment.

岩浆系统中金属元素的迁移和隔离调节了火山排放和矿床的发展的环境影响（Edmonds等，2022 Tattitch等，2021）。公共卫生机构归类为“环境污染物”的许多要素在硅酸盐融化中挥发了（Ilyinskaya等，2021）。不同构造环境中的火山发出对比痕量金属“指纹”，这与蒸气和硫化物饱和度相对时机的差异有关（Edmonds等，2018）。弧火山爆发岩浆，其中包含各种原代水含量，跨越1 wt％至7 wt％H2O，是从地幔源和俯冲贡献中的异质性继承的（Plank等，2013 Ruscitto等人，2012）。岩浆水含量会影响硅酸盐融化的物理和化学特性（例如粘度和结晶动力学），因此是对蒸气饱和度的时机/压力的关键控制 - 因此，痕量元素可以根据其融合式分隔系数的含量元素进行痕量元素，以分配为20的条件。然而，原始水含量在金属分配中的作用尚未有系统地研究。该项目分别确定了两个弧线火山 - 火山 - 火山 - 帕亚加，危地马拉，危地马拉，低下Andhigh Andhigh Magmatic水内容物（Lloyd等，2014 Walker等人，2003年）。跨越的目的是使用既定的岩石学策略重建和比较其痕量金属货物的演变。针对Fuego和Pacaya进行最终成员的比较，可以避免引入可能影响金属行为的其他不确定性，例如沿ARC或ARC Inter-Arc Inter-ARC变化。这项研究将涉及爆发的岩石和气羽中发出的金属气溶胶的现场采样。实验室工作将集中于对熔体夹杂物和眼镜的岩石学分析，包括对挥发性含量的离子探针分析，以及对过滤器收集的羽流气溶胶样品的地球化学分析。岩石学和热力学建模将提供一个框架来解释我们的地球化学数据，尤其是将金属行为与结晶过程和硅酸盐融化中溶解挥发相的组成相关联。该项目还将探索开发非传统方法来评估火山排放的环境影响的潜力：尤其是在植被，土壤和水文样品中使用微量金属的可行性，以评估火山痕量金属污染物对环境的递送机制和途径，以及对生态学科学和Hazard评估的影响。