Highly explosive basaltic eruptions driven by CO2 exsolution

Chelsea M Allison,Kurt Roggensack,Amanda B Clarke

doi:10.1038/s41467-020-20354-2

Chelsea M Allison, Kurt Roggensack + Show 1 more

Open Access

https://doi.org/10.1038/s41467-020-20354-2

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Journal: Nature Communications	Publication Date: Jan 11, 2021
Citations: 25	License type: open-access

Affiliation: Arizona State University

Abstract

The most explosive basaltic scoria cone eruption yet documented (>20 km high plumes) occurred at Sunset Crater (Arizona) ca. 1085 AD by undetermined eruptive mechanisms. We present melt inclusion analysis, including bubble contents by Raman spectroscopy, yielding high total CO2 (approaching 6000 ppm) and S (~2000 ppm) with moderate H2O (~1.25 wt%). Two groups of melt inclusions are evident, classified by bubble vol%. Modeling of post-entrapment modification indicates that the group with larger bubbles formed as a result of heterogeneous entrapment of melt and exsolved CO2 and provides evidence for an exsolved CO2 phase at magma storage depths of ~15 km. We argue that this exsolved CO2 phase played a critical role in driving this explosive eruption, possibly analogous to H2O exsolution driving silicic caldera-forming eruptions. Because of their distinct gas compositions relative to silicic magmas (high S and CO2), even modest volume explosive basaltic eruptions could impact the atmosphere.

Highlights

The most explosive basaltic scoria cone eruption yet documented (>20 km high plumes) occurred at Sunset Crater (Arizona) ca. 1085 AD by undetermined eruptive mechanisms
It has recently been documented as the most explosive scoria cone eruption identified on Earth to date[1], but the driving mechanism of such highly explosive basaltic eruptions is unclear[3]
One approach to determine melt inclusions (MIs) bubble contents is in situ measurement by Raman spectroscopy[17,18,20,24]

Summary

Introduction

The most explosive basaltic scoria cone eruption yet documented (>20 km high plumes) occurred at Sunset Crater (Arizona) ca. 1085 AD by undetermined eruptive mechanisms. MIs, are susceptible to modification from post-entrapment crystallization and shrinkage[14] during ascent, eruption, and quench at the surface[13], which often results in significant CO2 loss to a bubble within the MI (Fig. 1a)[15,16,17,18,19,20,21].

Results

Conclusion