Reconstructing Magma Storage Depths for the 2018 Kīlauean Eruption from Melt inclusion CO2 Contents: The Importance of Vapor Bubbles

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Authors

Penny E Wieser , Hector Lamadrid , John Maclennan, Marie Edmonds, Simon Matthews , Kayla Iacovino, Frances Jenner, Cheryl Gansecki, Frank Trusdell, R Lopaka Lee, Evgenia Ilyinskaya

Abstract

The 2018 lower East Rift Zone (LERZ) eruption and the accompanying collapse of the summit caldera marked the most destructive episode of activity at Kīlauea Volcano in the last 200 years. The eruption was extremely well-monitored, with extensive real-time lava sampling as well as continuous geodetic data capturing the caldera collapse. This multi-parameter dataset provides an exceptional opportunity to determine the reservoir geometry and magma transport paths supplying Kīlauea’s LERZ. The forsterite contents of olivine crystals, together with the degree of major element disequilibrium with carrier melts, indicates that two distinct crystal populations were erupted from Fissure 8 (termed High- and Low-Fo). Melt inclusion entrapment pressures reveal that Low-Fo olivines (close to equilibrium with their carrier melts) crystallized within the Halema’uma’u reservoir (~2 km depth), while many High-Fo olivines (>Fo81.5; far from equilibrium with their carrier melts) crystallized within the South Caldera reservoir (~3-5 km depth). Melt inclusions in High-Fo olivines experienced extensive post-entrapment crystallization following their incorporation into cooler, more evolved melts. This favoured the growth of a CO2-rich vapor bubble, containing up to 99% of the total melt inclusion CO2 budget (median=93%). If this CO2-rich bubble is not accounted for, entrapment depths are significantly underestimated. Conversely, reconstructions using equation of state methods rather than direct measurements of vapor bubbles overestimate entrapment depths. Overall, we show that direct measurements of melts and vapor bubbles by SIMS and Raman Spectroscopy, combined with a suitable H2O-CO2 solubility model, is a powerful tool to identify the magma storage reservoirs supplying volcanic eruptions

DOI

https://doi.org/10.31223/X5X60V

Subjects

Earth Sciences

Keywords

SIMS, Basaltic Volcanism, Raman Spectroscopy, Volatile Solubility

Dates

Published: 2020-12-05 20:04

Last Updated: 2021-01-07 08:05

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License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
The melt inclusion and glass compositions presented in this paper are provided as an excel spreadsheet. This data has been uploaded to the Cambridge University Repository \url{https://doi.org/10.17863/CAM.60202}, and is also available on Github \url{https://github.com/PennyWieser/G3-2018-MI}. This spreadsheet also contains the results of the bubble growth models shown in Fig. 9.

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