Heterogeneous vesiculation of 2011 El Hierro xeno-pumice revealed by X-ray computed microtomography

Margherita Polacci, Fabio Arzilli, S. E. Berg, V. R. Troll, F. M. Deegan, S Burchardt, M. Krumbholz, L. Mancini, J. C. Carracedo, F Brun

    Research output: Contribution to journalArticlepeer-review

    Abstract

    During the first week of the 2011 El Hierro submarine eruption, abundant light-coloured pumiceous, high-silica volcanic bombs coated in dark basanite were found floating on the sea. The composition of the light-coloured frothy material ("xeno-pumice") is akin to that of sedimentary rocks from the region, but the textures resemble felsic magmatic pumice, leaving their exact mode of formation unclear. To help decipher their origin, we investigated representative El Hierro xeno-pumice samples using X-ray computed microtomography for their internal vesicle shapes, volumes and bulk porosity, as well as for the spatial arrangement and size distributions of vesicles in three dimensions (3D). We find a wide range of vesicle morphologies, which are especially variable around small fragments of rock contained in the xeno-pumice samples. Notably, these rock fragments are almost exclusively of sedimentary origin, and we therefore interpret them as relicts of the original sedimentary ocean crust protolith(s). The irregular vesiculation textures observed probably resulted from pulsatory release of volatiles from multiple sources during xeno-pumice formation, most likely by successive release of pore- and mineral-water during incremental heating of the sedimentary protoliths.
    Original languageEnglish
    JournalBulletin of Volcanology
    Volume78
    Issue number85
    Early online date14 Nov 2016
    DOIs
    Publication statusPublished - Dec 2016

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