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  • Floating stones off El Hierro (Canary Islands, Spain) [Elektronski vir] : the peculiar case of the October 2011 eruption
    Troll, Valentin R. ...
    The eruption that started off the south coast of El Hierro, Canary Islands, in October 2011 has emitted intriguing eruption products found floating in the sea. These speci- mens appeared as floating ... volcanic “bombs” that have in the meantime been termed “restingolites” (after the close-by village of La Restinga) and exhibit cores of white and5 porous pumice-like material. Currently the nature and origin of these “floating stones” is vigorously debated among researchers, with important implications for the interpreta- tion of the hazard potential of the ongoing eruption. The “restingolites” have been pro- posed to be either (i) juvenile high-silica magma (e.g. rhyolite), (ii) remelted magmatic material (trachyte), (iii) altered volcanic rock, or (iv) reheated hyaloclastites or zeolite10 from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have collected and analysed the structure and composition of samples and compared the results to previous work on similar rocks found in the archipelago. Based on their high silica content, the lack of igneous trace element sig- natures, and the presence of remnant quartz crystals, jasper fragments and carbonate15 relicts, we conclude that “restingolites” are in fact xenoliths from pre-island sedimen- tary rocks that were picked up and heated by the ascending magma causing them to partially melt and vesiculate. They hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies in the Canary Islands as well as in similar Atlantic islands that rest on sediment/covered20 ocean crust (e.g. Cape Verdes, Azores). The occurrence of these “restingolites” does therefore not indicate the presence of an explosive high-silica magma that is involved in the ongoing eruption.
    Source: Solid earth discussions. - ISSN 1869-9537 (Vol. 3, 2011, str. 975-999)
    Type of material - e-article ; adult, serious
    Publish date - 2011
    Language - english
    COBISS.SI-ID - 138172419

    Link(s):

    https://se.copernicus.org/preprints/3/975/2011/sed-3-975-2011.pdf
    DOI

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