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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Finding eruptive mechanisms through pyroclasts from the current eruption (1984-present) at Nevado del Ruiz Volcanic Complex, Colombia
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Finding eruptive mechanisms through pyroclasts from the current eruption (1984-present) at Nevado del Ruiz Volcanic Complex, Colombia

机译：从哥伦比亚内瓦多·德尔·鲁伊斯火山群的当前喷发（1984年至今）中通过火山碎屑寻找爆发机制

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The dominant fragmentation mechanisms in the magma involved in a volcanic eruption can be understood from the compositional and textural analysis of the fragments emitted as pyroclasts. Individual pyroclasts can be juvenile, accessory and accidental, and detailed analyses of their relative proportions as well as the juvenile clast features can shed light into the fragmentation processes involved in the eruption. Despite the multiple (hundreds) eruptive pulses since the Nevado del Ruiz re-activation in 1984, following a quiescence of nearly 100 years, such analyses have not been carried out for the ash emissions preceding the recently emplaced plug. Here, four deposits related to the recent emissions were analysed from their pyroclasts. The samples correspond to eruptive pulses from the years 1985, 1986, 1988, and 2012. Their characterisation allowed proposing differences between likely juvenile fragments (i.e. representative of involved magma) and accessory fragments (i.e. pre-existing co-magmatic). The results indicate that alteration can be used as a criterion to distinguish them. Although this could not account for syn-eruptive hydrothermal alteration of juvenile glass, or for the preservation of accessory glass emplaced in glacial conditions, this criterion could serve as a foundation to direct fresh glass fragment analyses. Following this criterion, the fresh glass fragments, which are assumed to be juvenile fragments, are highly vesicular. They exhibit spongy and fibrous textures that are related to the predominant vesicle shape. Their predominance suggests a magmatic fragmentation mechanism, while blocky-shaped, poorly vesicular, cracked glass shards suggest a phreato-magmatic origin. Specifically, November of 1985 and January of 1986 glassy ashes are primarily highly vesicular, suggesting magmatic explosive events. By contrast, samples from the March of 1988 and May of 2012 events are primarily characterised by low fresh glass content. They also exhibit quenched surfaces, indicating that the magma-water interaction acted as an important factor for triggering the eruptive pulses. Real-time componentry, petrography, and glass characterisation in fine ash could significantly complement traditional geophysical monitoring, and importantly, improve the hazard assessments on the civil aviation during the ongoing Nevado del Ruiz activity. (C) 2018 Elsevier B.V. All rights reserved.
机译：火山喷发所涉及的岩浆中主要的碎裂机制可以从对以火山碎屑释放的碎片的组成和质地分析中了解。单个的破火山岩可能是幼年的，副生的和偶然的，并且对其相对比例以及幼年的碎屑特征的详细分析可以为爆发过程中的破碎过程提供启示。尽管自从1984年内瓦多·德尔·鲁伊斯（Nevado del Ruiz）重新激活以来已经历了多个（数百次）爆发脉冲，但经过了近100年的平静，但尚未对最近放置的塞子之前的灰分排放进行过此类分析。在这里，从它们的火山碎屑中分析了与最近排放有关的四个沉积物。样本对应于1985、1986、1988和2012年的爆发脉冲。它们的特征允许提出可能的幼年碎片（即所涉及的岩浆的代表）和副碎片（即预先存在的共岩浆）之间的差异。结果表明，改变可以用作区分它们的标准。尽管这不能解释青少年玻璃的协同水热变化，也不能解释冰河条件下放置的辅助玻璃的保存，但该标准可以作为指导新鲜玻璃碎片分析的基础。根据该标准，被认为是少年碎片的新鲜玻璃碎片是高度囊泡的。它们表现出与主要囊泡形状有关的海绵状和纤维状质地。它们的优势表明是岩浆碎裂的机制，而块状，囊泡较弱，破裂的玻璃碎片表明是岩浆岩浆的起源。具体而言，1985年11月和1986年1月的玻璃灰主要是囊泡状的，提示岩浆爆炸事件。相比之下，1988年3月和2012年5月事件的样品的主要特征是新鲜玻璃含量低。它们还表现出淬火的表面，表明岩浆-水的相互作用是触发喷发脉冲的重要因素。细灰中的实时成分，岩相学和玻璃特性可以大大补充传统的地球物理监测，并且重要的是，在正在进行的内华多德尔鲁伊斯活动期间，可以改善对民用航空的危害评估。 （C）2018 Elsevier B.V.保留所有权利。

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