Open AccessReconstructing Magma Storage Depths for the 2018 Kı̄lauean Eruption From Melt Inclusion CO 2 Contents: The Importance of Vapor Bubbles
Author(s) -
Wieser Penny E.,
Lamadrid Hector,
Maclennan John,
Edmonds Marie,
Matthews Simon,
Iacovino Kayla,
Jenner Frances E.,
Gansecki Cheryl,
Trusdell Frank,
Lee R.L.,
Ilyinskaya Evgenia
Publication year - 2021
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2020gc009364
Subject(s) - melt inclusions , geology , caldera , volcano , inclusion (mineral) , magma , lava , mineralogy , lava dome , olivine , phenocryst , geochemistry , petrology , volcanic rock
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 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 (>Fo 81.5 ; 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 favored the growth of a CO 2 ‐rich vapor bubble, containing up to 99% of the total melt inclusion CO 2 budget (median = 93%). If this CO 2 ‐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 H 2 O‐CO 2 solubility model, is a powerful tool to identify the magma storage reservoirs supplying volcanic eruptions.