权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Magma mush eruptibility: the lifetime of mobile magma

岩浆糊喷发性：移动岩浆的寿命

基本信息

批准号：
NE/T000430/1
负责人：
Madeleine Humphreys
金额：
$ 64.44万
依托单位：
Durham University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2020
资助国家：
英国
起止时间：
2020 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT000430%2F1
关键词：
Magma mush eruptibility lifetime mobile

项目摘要

Volcanism - the generation and eruption of molten rock from within the earth's interior - is one of the most visible manifestations of plate tectonics. Growth of the earth's crust occurs either when magma is stored and solidified within the crust, or is erupted at the earth's surface. Eruptive activity at subduction zones can be explosive and highly disruptive, and represents an important natural hazard, with implications for life, health and financial stability when it occurs. One of the major challenges facing volcanologists is the accurate forecasting of this eruptive behaviour. Abundant evidence of past volcanic activity shows that large volumes of magma can be erupted in a single event. However, geophysical techniques used to image below the earth's surface fail to distinguish large volumes of melt (magmatic liquid) stored within the crust. Instead, melt may be stored as "crystal mush", i.e. an accumulation of volcanic crystals separated by only small amounts of melt that is hard to image geophysically. However, a crystal mush with low melt content behaves like a solid and cannot be erupted. Researchers therefore suggest that the mush contains 'eruptible' lenses that have higher melt content, yet remain thin enough to be unresolved by geophysical techniques. If so, then wholesale spatial reorganisation of crystals and liquid in the whole mushy region could change its overall physical behaviour, such that it quickly becomes eruptible. In contrast, other scholars predict a prolonged existence of more liquid-rich (potentially eruptible) mush bodies within the crust. In this case, the lack of currently observed geophysical signals for large, melt-rich magma bodies may simply result from the ephemeral nature of magmatism. To make progress, more information about the longevity of eruptible mushy regions is essential. This proposal will develop a new method to determine the lifetime of melt-rich regions, enabling us to resolve this current conflict. Time 'chronology' information about volcanic systems is commonly recorded in the mineral zircon, which contains radioactive elements that are sensitive to time. Zircon chronology shows that crystal mushes can persist over long time periods (e.g. 100s kyr), but these measurements hold significant uncertainties. The lifetime of the more eruptible, melt-rich 'mobile magma' is much harder to investigate, because it occurs at higher temperatures where zircon may not be stable. However, this information is a critical link between geophysical observations, which record a snapshot of the state of the earth's crust, and volcanology, which records information about magmatic processes over very long times. This project will develop a new method to determine the lifetime of mobile magma crystallisation directly by analysing crystals that grow from melt at high temperatures. Specifically, we will relate the aspect ratio (length/ width) of the silicate mineral plagioclase, which grows from almost all subduction zone magmas, to the time available for crystallisation. Our preliminary work suggests a strong relationship between aspect ratio and time for water-rich, silica-rich magmas that erupt at subduction zones. Using high-temperature experiments, analysis of well-dated plagioclase crystals, and mathematical approaches, the team will derive a universal relationship that can be applied to all magmatic environments. We will apply the method to intermediate subduction zone volcanic systems that have recent geophysical information, in order to re-evaluate the architecture of the subterranean magma plumbing systems. Finally, we will integrate our crystal-scale observations with existing geophysical information and chronology datasets, to bring new insights into the distribution of melt and our ability to see it geophysically. This will lead to novel constraints on the identification, recognition and definition of mushy plumbing systems in future.

火山作用--从地球内部产生和喷发熔岩--是板块构造最明显的表现之一。地壳的生长要么发生在岩浆在地壳内储存和固化的时候，要么发生在地球表面喷发。俯冲区的喷发活动可能是爆炸性的和极具破坏性的，是一种重要的自然灾害，当它发生时，会对生命、健康和金融稳定产生影响。火山学家面临的主要挑战之一是准确预测这种喷发行为。过去火山活动的大量证据表明，大量岩浆可以在一次事件中喷发。然而，用于在地球表面下成像的地球物理技术无法区分储存在地壳内的大量熔体(岩浆液体)。相反，熔体可能以“晶体泥”的形式储存，即火山晶体的堆积被少量的熔体隔开，这在地球物理上很难成像。然而，熔体含量低的晶体糊状物的行为就像固体一样，不能喷发。因此，研究人员认为，泥浆中含有“可喷发”的透镜，这些透镜的熔体含量较高，但仍然很薄，无法通过地球物理技术解决。如果是这样，那么整个糊状区域的晶体和液体的大规模空间重组可能会改变它的整体物理行为，以至于它很快就会喷发。相比之下，其他学者预测，地壳内将长期存在更多富含液体(可能会喷发)的糊状天体。在这种情况下，目前观测到的大型富含熔体的岩浆体的地球物理信号的缺乏可能只是由于岩浆活动的短暂性质。为了取得进展，更多关于可喷发泥泞地区寿命的信息是必不可少的。这项提议将开发一种新的方法来确定富熔体区域的寿命，使我们能够解决目前的冲突。有关火山系统的时间“年表”信息通常记录在矿物锆石中，其中含有对时间敏感的放射性元素。锆石年代学表明，晶体泥可以持续很长一段时间(例如100s KYR)，但这些测量具有重大的不确定性。更容易喷发、富含熔体的“流动岩浆”的寿命要难得多，因为它发生在较高的温度下，那里的锆石可能不稳定。然而，这些信息是地球物理观测和火山学之间的关键联系，前者记录了地壳状态的快照，后者记录了很长一段时间内岩浆过程的信息。该项目将开发一种新的方法，通过分析高温下熔体生长的晶体，直接确定流动岩浆结晶的寿命。具体地说，我们将把几乎所有俯冲带岩浆中生长的硅酸盐矿物斜长石的长宽比(长/宽)与可结晶的时间联系起来。我们的初步工作表明，在俯冲带喷发的富水、富硅岩浆的纵横比与时间之间存在很强的关系。通过高温实验、对测年准确的斜长石晶体的分析和数学方法，该团队将推导出一个可以应用于所有岩浆环境的普遍关系。我们将把这种方法应用于拥有最新地球物理信息的中间俯冲带火山系统，以重新评估地下岩浆管道系统的架构。最后，我们将把晶体尺度的观测与现有的地球物理信息和年代学数据集结合起来，为熔体的分布和我们从地球物理上观察熔体的能力带来新的见解。这将导致未来对糊状管道系统的识别、识别和定义产生新的限制。