Melt inclusion constraints on petrogenesis of the 2014–2015 Holuhraun eruption, Iceland

Hartley, Margaret E. and Bali, Enikö and Maclennan, John and Neave, David A. and Halldórsson, Sæmundur A. (2018) Melt inclusion constraints on petrogenesis of the 2014–2015 Holuhraun eruption, Iceland. Contributions to Mineralogy and Petrology, 173 (2). ISSN 0010-7999 (Print) 1432-0967 (Online) DOI https://doi.org/10.1007/s00410-017-1435-0

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Official URL: http://doi.org/10.1007/s00410-017-1435-0

Abstract

The 2014–2015 Holuhraun eruption, on the Bárðarbunga volcanic system in central Iceland, was one of the best-monitored basaltic fissure eruptions that has ever occurred, and presents a unique opportunity to link petrological and geochemical data with geophysical observations during a major rifting episode. We present major and trace element analyses of melt inclusions and matrix glasses from a suite of ten samples collected over the course of the Holuhraun eruption. The diversity of trace element ratios such as La/Yb in Holuhraun melt inclusions reveals that the magma evolved via concurrent mixing and crystallization of diverse primary melts in the mid-crust. Using olivine–plagioclase–augite–melt (OPAM) barometry, we calculate that the Holuhraun carrier melt equilibrated at 2.1 ± 0.7 kbar (7.5 ± 2.5 km), which is in agreement with the depths of earthquakes (6 ± 1 km) between Bárðarbunga central volcano and the eruption site in the days preceding eruption onset. Using the same approach, melt inclusions equilibrated at pressures between 0.5 and 8.0 kbar, with the most probable pressure being 3.2 kbar. Diffusion chronometry reveals minimum residence timescales of 1–12 days for melt inclusion-bearing macrocrysts in the Holuhraun carrier melt. By combining timescales of diffusive dehydration of melt inclusions with the calculated pressure of H2O saturation for the Holuhraun magma, we calculate indicative magma ascent rates of 0.12–0.29 m s−1. Our petrological and geochemical data are consistent with lateral magma transport from Bárðarbunga volcano to the eruption site in a shallow- to mid-crustal dyke, as has been suggested on the basis of seismic and geodetic datasets. This result is a significant step forward in reconciling petrological and geophysical interpretations of magma transport during volcano-tectonic episodes, and provides a critical framework for the interpretation of premonitory seismic and geodetic data in volcanically active regions.

Item Type: Article
Uncontrolled Keywords: 2018AREP; IA74
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
07 - Gold Open Access
Journal or Publication Title: Contributions to Mineralogy and Petrology
Volume: 173
Identification Number: https://doi.org/10.1007/s00410-017-1435-0
Depositing User: Sarah Humbert
Date Deposited: 04 May 2018 16:51
Last Modified: 04 May 2018 16:51
URI: http://eprints.esc.cam.ac.uk/id/eprint/4262

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