Integrated petrological and geophysical constraints on magma system architecture in the western Galápagos Archipelago: insights from Wolf volcano

Stock, Michael J. and Bagnardi, Marco and Neave, David A. and Maclennan, John and Bernard, Benjamin and Buisman, Iris and Gleeson, Matthew L.M. and Geist, Denis (2018) Integrated petrological and geophysical constraints on magma system architecture in the western Galápagos Archipelago: insights from Wolf volcano. Geochemistry Geophysics Geosystems. ISSN 1525-2027

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Abstract

The 2015 eruption of Wolf volcano was one of the largest eruptions in the Galápagos Islands since the onset of routine satellite-based volcano monitoring. It therefore provides an excellent opportunity to combine geophysical and petrological data, to place detailed constraints on the architecture and dynamics of sub-volcanic systems in the western archipelago. We present new geodetic models which show that pre-eruptive inflation at Wolf was caused by magma accumulation in a shallow flat-topped reservoir at ~1.1 km, whereas edifice-scale deformation during the eruption was related to a deflationary source at 6.1–8.8 km. Petrological observations suggest that the erupted material was derived from both a sub-volcanic mush and a liquid-rich magma body. Using a combination of olivine-plagioclase-augite-melt (OPAM) and clinopyroxene-melt barometry, we show that the majority of magma equilibration, crystallisation and mush entrainment occurred at a depth equal to or greater than the deep geodetic source, with little petrological evidence of material sourced from shallower levels. Hence, our multidisciplinary study does not support a fully trans-crustal magmatic system beneath Wolf volcano before the 2015 eruption, but instead indicates two discrete storage regions, with a small magma lens at shallow levels and the major zone of magma storage in the lower crust, from which most of the erupted material was sourced. A predominance of lower crustal magma storage has previously been thought typical of sub-volcanic systems in the eastern Galápagos Archipelago, but our new data suggest that this may also occur beneath the more active volcanoes of the western archipelago.

Item Type: Article
Uncontrolled Keywords: 2018AREP; IA74
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
08 - Green Open Access
12 - PhD
Journal or Publication Title: Geochemistry Geophysics Geosystems
Depositing User: Sarah Humbert
Date Deposited: 07 Dec 2018 14:23
Last Modified: 12 Sep 2019 09:41
URI: http://eprints.esc.cam.ac.uk/id/eprint/4372

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