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Cryptic evolved melts beneath monotonous basaltic shield volcanoes in the Galápagos Archipelago.

Accepted version
Peer-reviewed

Type

Article

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Authors

Geist, Dennis 
Gleeson, Matthew LM  ORCID logo  https://orcid.org/0000-0003-0839-5492
Bernard, Benjamin 

Abstract

Many volcanoes erupt compositionally homogeneous magmas over timescales ranging from decades to millennia. This monotonous activity is thought to reflect a high degree of chemical homogeneity in their magmatic systems, leading to predictable eruptive behaviour. We combine petrological analyses of erupted crystals with new thermodynamic models to characterise the diversity of melts in magmatic systems beneath monotonous shield volcanoes in the Galápagos Archipelago (Wolf and Fernandina). In contrast with the uniform basaltic magmas erupted at the surface over long timescales, we find that the sub-volcanic systems contain extreme heterogeneity, with melts extending to rhyolitic compositions. Evolved melts are in low abundance and large volumes of basalt flushing through the crust from depth overprint their chemical signatures. This process will only maintain monotonous activity while the volume of melt entering the crust is high, raising the possibility of transitions to more silicic activity given a decrease in the crustal melt flux.

Description

Keywords

Igneous petrology, Volcanology, Galapagos, Geochemistry, Basalt

Journal Title

Nat Commun

Conference Name

Journal ISSN

2041-1723
2041-1723

Volume Title

11

Publisher

Springer Science and Business Media LLC

Rights

All rights reserved
Sponsorship
NERC (1772906)
NERC (NE/L002507/1)
Christ's College (Cambridge), National Science Foundation, University of Manchester, Jeremy Willson Charitable Trust, Mineralogical Society of Great Britain and Ireland