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Quantification of the intrusion process at Kīlauea volcano, Hawai'i

Journal of Volcanology and Geothermal Research
By:  and 
https://doi.org/10.1016/j.jvolgeores.2016.09.019

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Abstract

The characteristic size of two types of intrusions identified beneath Kīlauea's East Rift zone are uniquely estimated by combining time constraints from fractional crystallization and the rates of magma solidification during cooling. Some intrusions were rapidly emplaced as dikes, but stalled before reaching the surface, and cooled and crystallized to feed later fractionated eruptions. More specifically, using the observed time interval between initial emplacement and eruption of fractionated lava, whose degree of fractionation is estimated from petrologic mixing calculations, the extent of solidification or cooling needed to produce this amount of fractionation can be directly inferred. And from the known erupted volumes the spatial extent or size of this fractionated volume can be analytically related to the full size of the source body itself. Two examples yield dike widths of 82 and 68 m. Other intrusions remain close to the east rift magma transport path and are observed to last for decades or longer as viable magma bodies that may participate in feeding later eruptions. The thickness of semi-permanent reservoirs near the East Rift Zone magma transport path can be estimated by assuming a resupply rate that is sufficiently frequent to restrict cooling to < 10 °C. It is inferred that both types of intrusions likely began as dike offshoots from the East Rift Zone magma transport path, but the frequently resupplied bodies may have later been converted to sills or laccoliths of heights estimated at 43–62 m. Our modeled intrusions contrast with models of rapidly emplaced thinner dikes feeding shallow intrusions, which are accompanied by intense rift earthquake swarms and are often associated with eruptions.
These calculations show that long-term heating of the wallrock of the magma transport paths serves to slow conduit cooling, which may be partly responsible for sustaining long East Rift Zone eruptions. Adjacent to the vertical transport path beneath Kīlauea's summit, the combined effects of heating and ever-increasing magma supply rate may have forced a commensurate enlarging of the conduit, perhaps explaining the occurrence of a temporary burst of deep (5–15 km) long-period earthquake swarms between 1987 and 1992.

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Publication type Article
Publication Subtype Journal Article
Title Quantification of the intrusion process at Kīlauea volcano, Hawai'i
Series title Journal of Volcanology and Geothermal Research
DOI 10.1016/j.jvolgeores.2016.09.019
Volume 328
Year Published 2016
Language English
Publisher Elsevier
Contributing office(s) Volcano Science Center
Description 11 p.
First page 34
Last page 44
Country United States
State Hawaii
Other Geospatial East Rift zone of Kīlauea volcano
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