Melt inclusion vapour bubbles: the hidden reservoir for major, trace and volatile elements.
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| Authors: | Venugopal, S; Schiavi, F; Moune, S; Bolfan-Casanova, N; Druitt, T; Williams-Jones, G |
| Year: | 2020 |
| Journal: | Nature Scientific Reports 10, 9034 PDF Article Link (DOI) |
| Title: | Melt inclusion vapour bubbles: the hidden reservoir for major, trace and volatile elements. |
| Abstract: | Olivine-hosted melt inclusions (MIs) provide samples of magmatic liquids and their dissolved volatiles from deep within the plumbing system. Inevitable post-entrapment modifcations can lead to signifcant compositional changes in the glass and/or any contained bubbles. Re-heating is a common technique to reverse MI crystallisation; however, its efect 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 fuid 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 difusion 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 signifcantly underestimates the original magma composition and storage parameters. |
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