Melt inclusion vapour bubbles: the hidden reservoir for major and volatile elements
Melt inclusion vapour bubbles: the hidden reservoir for major and volatile elements
复制标题
熔体包裹体气泡：主要元素和挥发性元素的隐藏库
作者：
S. Venugopal;F. Schiavi;S. Moune;N. Bolfan;T. Druitt;G. Williams
橄榄岩中的熔融包裹体（MI）提供了来自管道系统深处的岩浆液体及其溶解挥发物的样品。不可避免的包埋后改性可导致玻璃和/或任何所含气泡的显著组成变化。再加热是逆转MI结晶的常用技术;然而，其对挥发物含量的影响被认为是轻微的。我们测试这一假设，使用结晶和玻璃质玄武岩MI，结合拉曼光谱和三维成像，调查流体和固体相的变化之前和之后的气泡重新加热。在重新加热之前，气泡含有CO2气体和硬石膏（CaSO 4）微晶。在再加热过程中，主要和挥发性元素从熔体中快速扩散，在气泡内产生新的相：SO2、石膏、铁硫化物。天然玻璃质MI中的蒸汽泡同样含有大量固相（碳酸盐、硫酸盐和硫化物），占MI总硫的84%，CO2的80%和FeO的14%。在再加热和天然玻璃质的MI中，气泡隔离了主要和挥发性元素，这些元素是总岩浆预算的组成部分，代表了玻璃的“损失”。仅对玻璃的分析大大低估了原始岩浆的成分和储存参数。
Olivine-hosted melt inclusions (MIs) provide samples of magmatic liquids and their dissolved volatiles from deep within the plumbing system. Inevitable post-entrapment modifications can lead to significant compositional changes in the glass and/or any contained bubbles. Re-heating is a common technique to reverse MI crystallisation; however, its effect on volatile contents has been assumed to be minor. We test this assumption using crystallised and glassy basaltic MIs, combined with Raman spectroscopy and 3D imaging, to investigate the changes in fluid and solid phases in the bubbles before and after re-heating. Before re-heating, the bubble contains CO2 gas and anhydrite (CaSO4) crystallites. The rapid diffusion of major and volatile elements from the melt during re-heating creates new phases within the bubble: SO2, gypsum, Fe-sulphides. Vapour bubbles hosted in naturally glassy MIs similarly contain a plethora of solid phases (carbonates, sulphates, and sulphides) that account for up to 84% of the total MI sulphur, 80% of CO2, and 14% of FeO. In both re-heated and naturally glassy MIs, bubbles sequester major and volatile elements that are components of the total magmatic budget and represent a “loss” from the glass. Analyses of the glass alone significantly underestimates the original magma composition and storage parameters.
影响因子：
5.3
作者：
Hartley, Margaret E.;Maclennan, John;Thordarson, Thor
通讯作者：
Thordarson, Thor