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Deep and disturbed : conditions for formation and eruption of a mingled rhyolite at Ascension Island, south Atlantic.

Chamberlain, Katy and Barclay, Jenni and Preece, Katie and Brown, Richard and McIntosh, Iona and EIMF, (2020) 'Deep and disturbed : conditions for formation and eruption of a mingled rhyolite at Ascension Island, south Atlantic.', Volcanica., 3 (1). pp. 139-153.

Abstract

The generation of felsic melts (through open or closed system processes) within ocean island volcanoes has been a key area of study since their identification. At Ascension Island in the south Atlantic, explosively erupted felsic melts have, to date, demonstrated a marked absence of signs of magma mixing and crustal assimilation. Here we present the first observations of a fall deposit from Ascension Island recording both macro- and micro-scale evidence for magma mingling. Geochemical analyses of mineral and glass phases, coupled with volatile concentrations of melt inclusions highlight the role of lower-crustal partial melting to produce rhyolitic magmas. Glass textures and the lack of zoning in major mineral phases indicate that mingling with a mafic melt occurred shortly prior to eruption. These inferences of a deep rhyolite production zone, coupled with rapid ascent rates highlight the challenges in forecasting a similar style of eruption at Ascension Island in the future.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.30909/vol.03.01.139153
Publisher statement:© The Author(s) 2020. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use,distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Date accepted:No date available
Date deposited:15 May 2020
Date of first online publication:05 May 2020
Date first made open access:15 May 2020

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