Conditions for nanocrystals formation in Krafla shallow rhyolitic magma: A potential site for explosive eruptions

克拉夫拉浅层流纹质岩浆中纳米晶体形成的条件：爆发性喷发的潜在地点

• 批准号: 457579444
• 负责人: Dr. Francisco Cáceres Acevedo
• 金额: --
• 依托单位: Sektion Mineralogie, Petrologie und Geochemie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2021
• 资助国家: 德国
• 起止时间: 2020-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/457579444?language=en
• 关键词: Conditions; nanocrystals; formation; Krafla; shallow

Krafla rhyolitic magma encountered at ~2100 m depth by wells related to geothermal exploration, in the frame of the IDDP project, opened new possibilities for unique research on magma reservoirs. The Krafla Magma Drilling Project (KMDP), within the priority program ICDP, was created to comprehend the origin as well as the physical, chemical and mechanical conditions of this magma under Krafla caldera. However, of great importance is to understand under what conditions this magma may erupt, which is the main objective that this project aims to contribute to resolve.The project presented here is born as a novel idea based on recent results on the effect of nanocrystals on degassing and viscosity changes of Krafla rhyolitic magma, and silicic magma in general, and the implications for eruption explosivity these nanocrystals have. Magmatic nanocrystals or “nanolites” are a yet underreported phenomenon that has been shown crucial to determine explosivity of magma in volcanic eruptions. However, the mostly unknown conditions at which these magmatic crystals form and remain stable create the need to investigate their capacity to form in the rhyolitic magma at Krafla for the potential explosivity that may induce.The general objective of this project is to determine the stability field and conditions required to form and sustain magmatic nanocrystals in pre- and (potential) syn-eruptive magma of Krafla, and the changes that these produce in magma properties. This will be studied through two experimental approaches, mimicking the conditions at which Krafla magma is stored. The oxidation state, pressure, temperature and time required to form and keep stable nanolites will be determined by performing highly controlled crystallisation experiments during magma cooling and stabilisation at variable P-T-t conditions using Krafla rhyolite material. Resultant material will be precisely analysed using cutting-edge methods to determine the presence, nature and extent of nanolites crystallisation. Rheology measurements will be performed to determine the extent of viscosity increase produced by different degree of nanolite crystallisation. Additionally, the physical process driving nanolite crystallisation from magma will be determined, i.e. crystallisation from a homogeneous liquid or immiscible liquids separation.Preliminary work shows that nanolites can form in rhyolitic magma from Krafla. However, it is expected as a main outcome from this project to stablish a complete map of conditions suitable for nanolites crystallisation, unveiling a critical aspect of this magma not explored beforehand.

在IDDP项目的框架内，与地热勘探有关的威尔斯井在~2100 m深处遇到的Krafla流纹岩岩浆为岩浆储层的独特研究开辟了新的可能性。在ICDP优先项目中，创建了Krafla岩浆钻探项目（KMDP），以了解Krafla火山口下岩浆的起源以及物理，化学和机械条件。然而，最重要的是了解在什么条件下岩浆可能喷发，这是本项目的主要目标，旨在帮助解决。这里提出的项目是一个新的想法，基于最近的结果，对克拉弗拉流纹岩岩浆和一般的岩浆的脱气和粘度变化的影响，以及这些纳米晶体对喷发爆炸性的影响。岩浆纳米晶体或“纳米晶体”是一种尚未被充分报道的现象，它对确定火山爆发中岩浆的爆炸性至关重要。然而，这些岩浆晶体形成和保持稳定的条件大多是未知的，因此需要研究它们在克拉夫拉流纹岩岩浆中形成的能力，以确定可能引起的潜在爆炸性。（潜在的）同喷发的克拉弗拉岩浆，以及这些岩浆性质的变化。这将通过两种实验方法进行研究，模拟Krafla岩浆储存的条件。氧化态，压力，温度和时间所需的形成和保持稳定的纳米晶将通过执行高度控制的结晶实验期间岩浆冷却和稳定在可变的P-T-t条件下使用Krafla流纹岩材料。所得材料将使用尖端方法进行精确分析，以确定纳米晶结晶的存在，性质和程度。将进行流变学测量以确定由不同程度的纳米沸石结晶产生的粘度增加的程度。此外，将确定驱动岩浆中纳米石结晶的物理过程，即从均匀液体或不混溶液体分离结晶。初步工作表明，纳米石可以在克拉弗拉流纹质岩浆中形成。然而，作为该项目的主要成果，预计将建立一个适合纳米结晶的完整地图，揭示这种岩浆的一个关键方面，而不是事先探索。