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

Chamberlain, Katy; Barclay, Jenni; Preece, Katie; Brown, Richard; McIntosh, Iona; EIMF

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.

Citation

Chamberlain, K., Barclay, J., Preece, K., Brown, R., McIntosh, I., & EIMF. (2020). Deep and disturbed: conditions for formation and eruption of a mingled rhyolite at Ascension Island, south Atlantic. Volcanica, 3(1), 139-153. https://doi.org/10.30909/vol.03.01.139153

• Journal Article Type: Article
• Online Publication Date: May 5, 2020
• Publication Date: 2020
• Deposit Date: May 15, 2020
• Publicly Available Date: May 15, 2020
• Journal: Volcanica
• Electronic ISSN: 2610-3540
• Publisher: Volcanica
• Peer Reviewed: Peer Reviewed
• Volume: 3
• Issue: 1
• Pages: 139-153
• DOI: https://doi.org/10.30909/vol.03.01.139153
• Public URL: https://durham-repository.worktribe.com/output/1270659