CO2 diffusion and degassing in volcanic melts

火山熔体中的 CO2 扩散和脱气

• 批准号: 509474999
• 负责人: Dr. Burkhard Schmidt
• 金额: --
• 依托单位: Abteilung Experimentelle und Angewandte Mineralogie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/509474999?language=en
• 关键词: CO2; diffusion; degassing; volcanic; melts

The eruptive behaviour of a volcano is heavily influenced by the volatiles of the magma (mainly H2O and CO2). During the ascent of a volatile rich magma, bubble nucleation and bubble growth can occur due to the decrease in pressure. Finally, an erupting magma can be fragmented, which results in explosive and dangerous volcanic eruptions. The aim of this research project is to contribute to the understanding of the degassing mechanisms of CO2-rich silicate melts. For that purpose, the mobility of CO2 in silicate melts (diffusion) as well as the degassing of CO2-rich melts will be investigated. Previous studies focussed on diffusion and degassing of H2O. Consequently, there is a need for experimental data on CO2, which represents the second most abundant volatile within magmatic melts. CO2 diffusion will be investigated via diffusion couple experiments at high pressure and high temperatures above the liquidus using an internally heated pressure vessel (IHPV). The melt compositions that will be used for the diffusion experiments are based on natural volcanic melts from Stromboli (basaltic), Popocatépetl (dacitic) and Vesuvius (phonolitic). Since H2O has a strong influence on CO2 diffusion and because it is often present in natural melts, the experiments will be performed using different H2O concentrations in the melts. As a result, the individual influences of different parameters (melt composition, H2O concentration, temperature) will be investigated systematically. The degassing behaviour of CO2-rich melts will be investigated via decompression experiments using the IHPV by simulating a magma ascent with different ascent rates. In order to investigate the degassing of CO2, the experiments will be performed using nominally H2O-free melts. Decompression experiments will be performed using the same basaltic and phonolitic melts that were previously used in diffusion experiments. The experiments will especially shed light on processes of bubble nucleation and bubble growth. The effects of decompression rate and melt composition will be evaluated. Information on diffusion and degassing is important for modelling magma ascent and predicting volcanic eruptions based on volcanic gas emissions. The obtained experimental data will also allow a comparison with the diffusion and degassing behaviour of other volatiles (mainly H2O) for a better understanding of natural volcanic systems.

火山的喷发行为很大程度上受到岩浆挥发物(主要是水和二氧化碳)的影响。在富含挥发性岩浆的上升过程中，由于压力的降低，可能会发生气泡成核和气泡生长。最后，喷发的岩浆可能碎裂，从而导致爆炸性和危险的火山喷发。这一研究项目的目的是为了有助于理解富CO2硅酸盐熔体的脱气机理。为此，将研究二氧化碳在硅酸盐熔体中的迁移(扩散)以及富含二氧化碳的熔体的脱气。以往的研究主要集中在H2O的扩散和脱气。因此，需要关于二氧化碳的实验数据，二氧化碳是岩浆熔体中第二丰富的挥发性物质。二氧化碳扩散将通过使用内部加热压力容器(IHPV)在高压和高温下在液相线上方进行扩散耦合实验来研究。将用于扩散实验的熔体成分是基于来自Stromboli(玄武岩)、Popocatépetl(英安岩)和Vesuvius(声橄榄岩)的天然火山熔体。由于H2O对二氧化碳扩散有很强的影响，而且它经常存在于天然熔体中，因此实验将在熔体中使用不同的H2O浓度进行。因此，系统地研究了不同参数(熔体组成、H2O浓度、温度)对熔体性能的影响。富二氧化碳熔体的脱气行为将通过使用IHPV的减压实验来研究，该实验通过模拟不同上升速率的岩浆上升来进行。为了研究二氧化碳的脱气，将使用名义上不含水的熔体进行实验。减压实验将使用以前在扩散实验中使用的相同的玄武岩和声橄榄岩熔体进行。这些实验将特别阐明气泡成核和气泡生长的过程。将评估减压速度和熔体组成的影响。有关扩散和脱气的信息对于模拟岩浆上升和根据火山气体排放预测火山喷发很重要。获得的实验数据还将允许与其他挥发物(主要是H2O)的扩散和脱气行为进行比较，以更好地了解自然火山系统。