Time scales of magma transport and mixing at Kīlauea Volcano, Hawai’i

Auriol S.P Rae,Bruce Houghton,Marie Edmonds,Margaret E Hartley,Daniel Morgan,John Maclennan,Isobel Sides

doi:10.1130/g37800.1

Abstract

Modeling of volcanic processes is limited by a lack of knowledge of the time scales of storage, mixing, and final ascent of magmas into the shallowest portions of volcanic plumbing systems immediately prior to eruption. It is impossible to measure these time scales directly; however, micro-analytical techniques provide indirect estimates based on the extent of diffusion of species through melts and crystals. We use diffusion in olivine phenocrysts from the A.D. 1959 Kīlauea Iki (Hawai’i, USA) eruption to constrain the timing of mixing events in the crustal plumbing system on time scales of months to years before eruption. The time scales derived from zonation of Fe-Mg in olivines, combined with contemporaneous geophysical data, suggest that mixing occurred on three time scales: (1) as much as 2 yr prior to eruption in the deep storage system; (2) in a shallow reservoir, between incoming hot melts and resident melt for several weeks to months prior to eruption; and (3) in the conduit and summit reservoir, between the resident magma and cooled surface lava, draining back into the vent on time scales of hours to several days during pauses between episodes. Synchronous inflation of the shallow reservoir with deep earthquake swarms and mixing suggests an intermittently open transcrustal magmatic system.

Highlights

Modeling of volcanic processes is limited by a lack of knowledge of the time scales of stor- lent opportunity to retrospectively constrain the age, mixing, and final ascent of magmas into the shallowest portions of volcanic plumbing timing of magma ascent and mixing with respect systems immediately prior to eruption
A.D. 1959 Kīlauea Iki (Hawai’i, USA) eruption to constrain the timing of mixing events in the involved 17 episodes of eruption
Geophysical and geochemical observaderived from zonation of Fe-Mg in olivines, combined with contemporaneous geophysical tions suggest that magma stored in a shallow data, suggest that mixing occurred on three time scales: (1) as much as 2 yr prior to eruption reservoir was mixed, during and between epiin the deep storage system; (2) in a shallow reservoir, between incoming hot melts and resi- sodes, with primitive magmas from depth as dent melt for several weeks to months prior to eruption; and (3) in the conduit and summit well as with cooler, outgassed lava that had reservoir, between the resident magma and cooled surface lava, draining back into the vent drained back from a lava lake formed in epion time scales of hours to several days during pauses between episodes

Summary

Introduction

Modeling of volcanic processes is limited by a lack of knowledge of the time scales of stor- lent opportunity to retrospectively constrain the age, mixing, and final ascent of magmas into the shallowest portions of volcanic plumbing timing of magma ascent and mixing with respect systems immediately prior to eruption. A.D. 1959 Kīlauea Iki (Hawai’i, USA) eruption to constrain the timing of mixing events in the involved 17 episodes of eruption Time of Kīlauea Iki, Kīlauea Volcano, Hawai’i, USA These time scales are compared with the scales of magma movement through the litho- (Fig. 1), the type example of a powerful Hawai- timings of deformation and seismicity recorded sphere prior to eruptions are difficult to resolve ian fountaining eruption. It included the highest during the eruption. It has not been possible to state surements (Eaton et al, 1987), direct observation METHOD

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