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.
Original language | English |
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Pages (from-to) | 139-153 |
Number of pages | 15 |
Journal | Volcanica |
Volume | 3 |
Issue number | 1 |
DOIs | |
Publication status | Published - 5 May 2020 |
Keywords
- Ascension Island
- Crustal melting
- Magma genesis
- Magma mingling
Profiles
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Jenni Barclay
- School of Environmental Sciences - Professor of Volcanology
- Geosciences - Member
Person: Research Group Member, Academic, Teaching & Research