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

“地球上大多数陆上火山活动发生在火山弧上，那里发现了最具爆炸性的火山。弧火山的生长最终是由俯冲板片和弧下地幔中发生的岩浆过程驱动的，然而，在10 - 100 kyrs的时间尺度上，岩浆上升和喷发可能受到岩石圈构造或冰川活动等因素的影响。因此，了解这些火山的生长和喷发历史，需要了解弧岩浆活动的背景下，区域地球动力学和其他因素，可能会调节喷发活动。莫乔-乔舒恩科火山群位于智利南部火山区，有着频繁爆发的历史。熔岩和火山灰的成分从玄武岩到流纹岩不等，岩浆从各种喷口喷出，包括许多单成因火山锥。最近的研究2表明，冰川活动与冰去除后，最后一次冰期最大（在18万年）施加了强烈的控制喷发的成分从莫乔Choshuenco。这一火山系统对冰去除的拟议反应比以前对弧火山提出的反应更为微妙，3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与卸载相关的应力变化作出反应。调查的作用，气候变化在调制火山在Mocho-Choschuenco，和潜在的影响因素，如挥发物的流量到大气中，需要详细的源（S）和存储历史的关键冰后期喷发单位的特性。影响喷发活动的另一个因素是一个大型走滑断层系统的存在：液化-奥夫基断层带。这种大规模的弧内结构与火山活动沿着南部火山带4和Mocho-Choshuenco相互作用，似乎有助于在主要喷发口5观察到的不寻常的熔体成分的上升和喷发。本计画将应用地球化学、岩石学及同位素方法，探讨冰后期莫乔-乔舒恩科火山系统岩浆供应与储存的动力学。您将在智利进行实地考察，对关键的喷发单位进行采样，获得火山地形实地采样的技能。然后，您将设计和实施一个分析计划，旨在调查从不同喷发中取样的岩浆来源，并重建喷发前的存储动态和挥发性通量。将通过电子微探针分析玻璃和矿物成分，如果找到合适的样品，将申请在NERC离子微探针设施收集关于挥发物含量的数据。与此同时，将在利兹通过热电离质谱（TIMS）分析放射性同位素比值，调查与构造或冰川对岩浆作用的控制有关的地幔源参数的任何变化。地球化学分析的结果将被整合，以利用现有的岩石学建模工具或其他数值方法构建Mocho-Choshuenco的岩浆过程模型。"

"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. "