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Reconstructing Magma Storage Depths for the 2018 Kı̄lauean Eruption From Melt Inclusion CO2 Contents: The Importance of Vapor Bubbles

Accepted version
Peer-reviewed

Type

Article

Change log

Abstract

jats:titleAbstract</jats:title>jats:pThe 2018 lower East Rift Zone (LERZ) eruption and the accompanying collapse of the summit caldera marked the most destructive episode of activity at Kı̄lauea 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 multiparameter data set provides an exceptional opportunity to determine the reservoir geometry and magma transport paths supplying Kı̄lauea’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 (>Fojats:sub81.5</jats:sub>; 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 favored the growth of a COjats:sub2</jats:sub>‐rich vapor bubble, containing up to 99% of the total melt inclusion COjats:sub2</jats:sub> budget (median = 93%). If this COjats:sub2</jats:sub>‐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 secondary‐ion mass spectrometry and Raman spectroscopy, combined with a suitable Hjats:sub2</jats:sub>O‐COjats:sub2</jats:sub> solubility model, is a powerful tool to identify the magma storage reservoirs supplying volcanic eruptions.</jats:p>

Description

Keywords

Melt Inclusions, K&#299, lauea Volcano, Magma storage depths, Ocean Island Volcanism, Raman Spectroscopy, Petrology

Journal Title

Geochemistry, Geophysics, Geosystems

Conference Name

Journal ISSN

1525-2027
1525-2027

Volume Title

22

Publisher

American Geophysical Union (AGU)

Rights

All rights reserved
Sponsorship
NERC (1928862)
NERC (NE/L002507/1)
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