TY - JOUR

T1 - Integrated Petrological and Geophysical Constraints on Magma System Architecture in the Western Galápagos Archipelago: Insights From Wolf Volcano

AU - Stock, Michael J.

AU - Bagnardi, Marco

AU - Neave, David A.

AU - Maclennan, John

AU - Bernard, Benjamin

AU - Buisman, Iris

AU - Gleeson, Matthew L.M.

AU - Geist, Dennis

N1 - Funding information: M. J. S. was supported by a Charles Darwin and Galápagos Islands Junior Research Fellowship at Christ’s College, Cambridge. M. B. was supported by the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET) and by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by the Universities Space and Research Administration (USRA) through a contract with NASA. D. A. N. was supported by the Alexander von Humboldt Foundation and the German Research Foundation (NE 2097/1-1). M. L. M. G. was supported by a NERC studentship (NE/L002507/1). Additional fieldwork funding was provided by the Jeremy Willson Charitable Trust (administered by the Geological Society of London) and the Mineralogical Society of Great Britain and Ireland. Envisat data were provided by ESA through the GEO Geohazards Supersite (http://supersites.earthobservations.org). Sentinel-1 interferograms were derived from Copernicus SAR data obtained at https://schihub.copernicus.eu and maps in Figure 1 were created using JAXA ALOS imagery from http://www.eorc. jaxa.jp/. This work would not have been possible without significant support from the Charles Darwin Foundation and the Galápagos National Park. We are grateful to Sally Gibson and Antonio Proaño for their assistance in the field and Yu Zhou, Tui De Roy, and Gabriele Gentile for help with fieldwork planning and logistics. We thank David Anchundia for providing a visual report of the 2015 eruption and Roel van Elsas for mineral separation. The manuscript was greatly improved by constructive reviews from Keith Putirka and an anonymous reviewer. The data for this paper are available in the supporting information. M. J. S. was supported by a Charles Darwin and Gal?pagos Islands Junior Research Fellowship at Christ's College, Cambridge. M. B. was supported by the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET) and by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by the Universities Space and Research Administration (USRA) through a contract with NASA. D. A. N. was supported by the Alexander von Humboldt Foundation and the German Research Foundation (NE 2097/1-1). M. L. M. G. was supported by a NERC studentship (NE/L002507/1). Additional fieldwork funding was provided by the Jeremy Willson Charitable Trust (administered by the Geological Society of London) and the Mineralogical Society of Great Britain and Ireland. Envisat data were provided by ESA through the GEO Geohazards Supersite (http://supersites.earthobservations.org). Sentinel-1 interferograms were derived from Copernicus SAR data obtained at https://schihub.copernicus.eu and maps in Figure?1 were created using JAXA ALOS imagery from http://www.eorc.jaxa.jp/. This work would not have been possible without significant support from the Charles Darwin Foundation and the Gal?pagos National Park. We are grateful to Sally Gibson and Antonio Proa?o for their assistance in the field and Yu Zhou, Tui De Roy, and Gabriele Gentile for help with fieldwork planning and logistics. We thank David Anchundia for providing a visual report of the 2015 eruption and Roel van Elsas for mineral separation. The manuscript was greatly improved by constructive reviews from Keith Putirka and an anonymous reviewer. The data for this paper are available in the supporting information.

PY - 2019/1/15

Y1 - 2019/1/15

N2 - 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 subvolcanic systems in the western archipelago. We present new geodetic models that 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 subvolcanic 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, crystallization, 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 transcrustal 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 subvolcanic 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.

AB - 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 subvolcanic systems in the western archipelago. We present new geodetic models that 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 subvolcanic 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, crystallization, 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 transcrustal 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 subvolcanic 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.

KW - deformation

KW - Galapagos

KW - InSAR

KW - magma storage

KW - petrology

KW - Thermobarometry

UR - http://www.scopus.com/inward/record.url?scp=85059283731&partnerID=8YFLogxK

U2 - 10.1029/2018GC007936

DO - 10.1029/2018GC007936

M3 - Article

AN - SCOPUS:85059283731

VL - 19

SP - 4722

EP - 4743

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 12

ER -