Publication Date:
2021-06-25
Description:
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 resem-
bling 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.
results of our textural, mineralogical, elemental and isotopic analysis lead us to conclude that the early floating stones of
El Hierro are vesiculated crustal xenoliths that originate from the substantial layer of sub-volcanic pre-island sedimentary
rocks (layer 1 of the oceanic crust) that is present underneath the Canary archipelago.
Description:
The Swedish and the German
Science Foundations (VR and DFG), the ERC grant EVOKES
and the Center for Natural Disaster Science (CNDS) Sweden
Description:
Published
Description:
97-110
Description:
N/A or not JCR
Description:
open
Keywords:
El Hierro volcano
;
Canary Islands
;
04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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