Post-glacial magma dynamics at the Mocho-Choshuenco volcanic complex, Chile

智利 Mocho-Choshuenco 火山群的冰期后岩浆动力学

• 批准号: 2743371
• 金额: --
• 依托单位: University of Leeds
• 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-2743371
• 关键词: Post; glacial; magma; dynamics; Mocho

"Most subaerial volcanism on Earth occurs at volcanic arcs, where the most explosive volcanoes are found. The growth of an arc volcano is ultimately driven by magmatic processes occurring in the subducting slab and sub-arc mantle, however, over timescales of 10s-100s of kyrs, magma ascent and eruption can be influenced by factors such as lithospheric tectonics or glacial activity. Understanding the growth and eruptive history of these volcanoes therefore requires understanding arc magmatism within the context of both regional geodynamics and other factors that may modulate eruptive activity. The Mocho-Choshuenco volcanic complex, located in Chile's southern volcanic zone, has a history of frequent explosive eruptions1. Lava and tephra compositions vary from basaltic to rhyolitic, and magmas are erupted from a variety of vents, including numerous monogenetic cinder cones. Recent research2 suggests that glacial activity associated with ice removal after the last glacial maximum (at 18 ka) exerted a strong control on erupted compositions from Mocho-Choshuenco. The proposed response of this volcanic system to ice removal is more nuanced that previously suggested for arc volcanoes3 and involves transitions in the dynamics of crustal melt storage as the sub-volcanic plumbing system responds to the stress changes associated with unloading. Investigating the role climate variability in modulating volcanism at Mocho-Choschuenco, and the potential implications for factors such as the flux of volatiles to the atmosphere, requires detailed characterization of the source(s) and storage histories of key post-glacial eruptive units. A further factor influencing eruptive activity here is the presence of a large strike-slip fault system: the Liquine-Ofqui fault zone. This large-scale intra-arc structure interacts with volcanism along the southern volcanic zone4 and at Mocho-Choshuenco appears to facilitate the ascent and eruption of unusual melt compositions not observed at the main eruptive vents5. This project will apply geochemical, petrological, and isotopic methods to investigate the dynamics of magma supply and storage at Mocho-Choshuenco volcanic system during the post-glacial period. You will undertake fieldwork in Chile to sample key eruptive units, gaining skills in field sampling in volcanic terrains. You will then design and implement an analytical programme aimed at investigating the sources of magmas sampled from different eruptions and reconstructing pre-eruptive storage dynamics and volatile fluxes. Glass and mineral composition will be analysed via electron microprobe and, if suitable samples are found, an application made to collect data on volatile contents at the NERC Ion Microprobe Facility. In parallel, an investigation of any variations in mantle source parameters, associated with either tectonic or glacial controls on magmatism, will be investigated by analysis of radiogenic isotope ratios via thermal ionization mass spectrometry (TIMS) at Leeds. The results of the geochemical analysis will be integrated to construct models of magmatic processes at Mocho-Choshuenco using either available petrological modelling tools or other numerical methods. "

地球上大多数空中火山活动发生在火山弧上，那里发现了最具爆炸性的火山。弧形火山的生长最终是由俯冲板块和弧下地幔中发生的岩浆作用驱动的，然而，在10s-100s的时间尺度上，岩浆上升和喷发会受到岩石圈构造或冰川活动等因素的影响。因此，要了解这些火山的生长和喷发历史，就需要在区域地球动力学和可能调节喷发活动的其他因素的背景下了解弧岩浆作用。莫科-乔顺科火山复合体位于智利南部火山带，有频繁爆发的历史1。熔岩和火山灰的成分从玄武岩到流纹岩各不相同，岩浆从各种喷口喷发出来，包括许多单一成因的煤渣锥。最近的研究2表明，在最后一次冰盛期(18ka)之后，与冰移走有关的冰川活动对Mocho-ChoShuenco喷发的成分施加了强有力的控制。这一火山系统对除冰的拟议反应比以前对弧形火山3提出的反应更加细微，并涉及地壳熔体储存动力学的转变，因为次火山管道系统对卸荷相关的应力变化作出反应。要研究气候变化在调节莫乔-乔申科火山活动中的作用，以及对挥发物进入大气等因素的潜在影响，需要详细描述来源(S)和关键的冰川后喷发单元的储存史。影响这里喷发活动的另一个因素是存在一个大型走滑断裂系统：Liquine-Ofqui断裂带。这种大规模的弧内结构与南部火山带4和莫科-乔顺科的火山作用相互作用，似乎促进了主喷口没有观察到的异常熔体成分的上升和喷发。该项目将应用地球化学、岩石学和同位素方法来研究后冰期莫乔-乔顺科火山系统的岩浆供应和储存动力学。你将在智利从事实地工作，对关键的喷发单元进行采样，获得在火山地带进行实地采样的技能。然后，你将设计和实施一项分析方案，旨在调查从不同喷发中取样的岩浆的来源，并重建喷发前的储存动力学和挥发通量。玻璃和矿物成分将通过电子微探针进行分析，如果找到合适的样品，还将应用程序收集NERC离子微探针设施的挥发性成分数据。同时，将通过利兹的热电离质谱(TIMS)分析放射性同位素比率，调查与构造或冰川控制岩浆作用有关的地幔来源参数的任何变化。地球化学分析的结果将综合起来，利用现有的岩石学模拟工具或其他数值方法建立莫科-乔舒恩科的岩浆过程模型。“