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| Titel |
Floating stones off El Hierro, Canary Islands: xenoliths of pre-island sedimentary origin in the early products of the October 2011 eruption |
| VerfasserIn |
V. R. Troll, A. Klügel, M.-A. Longpré, S. Burchardt, F. M. Deegan, J. C. Carracedo, S. Wiesmaier, U. Kueppers, B. Dahren, L. S. Blythe, T. H. Hansteen, C. Freda, D. A. Budd, E. M. Jolis, E. Jonsson, F. C. Meade, C. Harris, S. E. Berg, L. Mancini, M. Polacci, K. Pedroza |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 3, no. 1 ; Nr. 3, no. 1 (2012-03-13), S.97-110 |
| Datensatznummer |
250000839
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| Publikation (Nr.) |
 copernicus.org/se-3-97-2012.pdf |
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| Zusammenfassung |
| A submarine eruption started off the south coast of El Hierro, Canary
Islands, on 10 October 2011 and continues at the time of this writing (February
2012). In the first days of the event, peculiar eruption products were found
floating on the sea surface, drifting for long distances from the eruption
site. These specimens, which have in the meantime been termed
"restingolites" (after the close-by village of La Restinga), appeared as
black volcanic "bombs" that exhibit cores of white and porous pumice-like
material. Since their brief appearance, the nature and origin of these
"floating stones" has been vigorously debated among researchers, with
important implications for the interpretation of the hazard potential of the
ongoing eruption. The "restingolites" have been proposed 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
zeolite from the submarine slopes of El Hierro.
Here, we provide evidence that supports yet a different conclusion. We have
analysed the textures and compositions of representative "restingolites"
and compared the results to previous work on similar rocks found in the
Canary Islands. Based on their high-silica content, the lack of igneous
trace element signatures, the presence of remnant quartz crystals, jasper
fragments and carbonate as well as wollastonite (derived from thermal
overprint of carbonate) and their relatively high oxygen isotope values, we
conclude that "restingolites" are in fact xenoliths from pre-island
sedimentary layers that were picked up and heated by the ascending magma,
causing them to partially melt and vesiculate. As they are closely
resembling pumice in appearance, but are xenolithic in origin, we refer to
these rocks as "xeno-pumice". The El Hierro xeno-pumices hence represent
messengers from depth that help us to understand the interaction between
ascending magma and crustal lithologies beneath the Canary Islands as well
as in similar Atlantic islands that rest on sediment-covered ocean crust
(e.g. Cape Verdes, Azores). The occurrence of "restingolites" indicates that crustal recycling is a relevant process in ocean islands,
too, but does not herald the arrival of potentially explosive high-silica
magma in the active plumbing system beneath El Hierro. |
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