Integrated Petrological and Geophysical Constraints on Magma System Architecture in the Western Galápagos Archipelago: Insights From Wolf Volcano
Geochemistry, Geophysics, Geosystems
Wiley for AGU
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Stock, M., Bagnardi, M., Neave, D., Maclennan, J., Bernard, B., Buisman, I., Gleeson, M., & et al. (2018). Integrated Petrological and Geophysical Constraints on Magma System Architecture in the Western Galápagos Archipelago: Insights From Wolf Volcano. Geochemistry, Geophysics, Geosystems, 19 (12), 4722-4743. https://doi.org/10.1029/2018GC007936
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 \char1261.1 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.
External DOI: https://doi.org/10.1029/2018GC007936
This record's URL: https://www.repository.cam.ac.uk/handle/1810/288324