Spatio-temporal evolution of crystal-mush horizons in the Icelandic crust - A case study of the northern segment of the Bárdarbunga volcanic system

冰岛地壳晶糊层的时空演化——以巴达本加火山系统北段为例

• 批准号: 415799836
• 负责人: Dr. Maren Kahl
• 金额: --
• 依托单位: Department of Earth Sciences
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/415799836?language=en
• 关键词: Spatio; temporal; evolution; crystal; mush

Classical views of magma storage in melt-dominated single chambers have been increasingly challenged by petrological and geophysical studies over the past three decades. The concept of vertically extensive ‘magma columns’ consisting of an intricate network of interconnected, multi-level magma storage horizons (sills) embedded in partially solidified crystal-mush zones is now considered more realistic. Crystal-mush zones are dynamic bodies comprising a rheologically ‘stiffer’ framework of crystal-mush with interspersed melt lenses of variable shape and size; the proportion of crystal to melt fractions within crystal-mush zones varies in both space and time. Although the existence of crystal-mush zones in the crust beneath the Icelandic Axial Rift is supported by many lines of evidence, our understanding remains limited. Nevertheless, the implications of its existence for the rapid generation and mobilisation of magma are highly significant. In order to address the role of crystal-mush zones in volcanism in Iceland we focus on the following key questions. (1) What is the nature of magma storage? (2) What is the vertical extent of the storage network? (3) What is the mush zone made of and how does it process magma? (4) What are the timescales of magma storage, processing, and mobilization? We will investigate these questions using an integrated approach linking textural data with state-of-the-art quantitative petrological-geochemical methods and high-precision diffusion modelling. Our approach will be applied to a unique suite of temporally and geochemically well-constrained tholeiitic basalts from the northern segment of the highly-active Bárðarbunga fissure swarm, one of Iceland’s most productive and largest volcanic systems. This 3-year project offers a novel, quantitative assessment of the spatial and temporal evolution of magma storage, accumulation, remobilisation and transfer through crystal-mush zones one the scale of Bárðarbunga fissure swarm. The proposed study will provide key insights into to the thickness, structure, composition and physical state of the mid- to lower oceanic crust and will consolidate our understanding of crustal accretion and formation in an active spreading margin.

在过去的三十年里，岩浆储存在熔体主导的单室中的经典观点越来越受到岩石学和地球物理学研究的挑战。垂直延伸的“岩浆柱”的概念，包括一个复杂的网络互连，多层次的岩浆存储层（底床）嵌入部分固化的晶体糊状区现在被认为是更现实的。晶体糊状物区是动态体，其包括晶体糊状物的流变学上“更硬”的框架，其中散布有形状和尺寸可变的熔体透镜;晶体糊状物区内晶体与熔体部分的比例在空间和时间上都不同。虽然冰岛轴向裂谷下方地壳中存在晶体泥带的说法得到了许多证据的支持，但我们的理解仍然有限。尽管如此，它的存在对岩浆的快速生成和流动的影响非常重要。为了解决冰岛火山活动中水晶泥区的作用，我们集中在以下关键问题。(1)岩浆储存的本质是什么？(2)存储网络的垂直范围是多少？(3)糊状区是由什么组成的，它是如何处理岩浆的？(4)岩浆储存、加工和流动的时间尺度是什么？我们将调查这些问题使用一个综合的方法，将纹理数据与最先进的定量岩石地球化学方法和高精度扩散建模。我们的方法将适用于一套独特的时间和地球化学约束拉斑玄武岩从北方段的高度活跃的Barrabuarbunga裂缝群，冰岛最多产和最大的火山系统之一。这个为期3年的项目提供了一个新的，定量评估的空间和时间演化的岩浆储存，积累，再动员和转移通过晶体糊状区的一个规模的Bárarbunga裂缝群。拟议的研究将提供关键的见解，以了解中下部洋壳的厚度、结构、组成和物理状态，并将巩固我们对活跃扩张边缘地壳增生和形成的理解。