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| Titel |
Spatial and temporal variations of diffuse CO2 degassing at the N-S
volcanic rift-zone of Tenerife (Canary Islands, Spain) during 2002-2015
period |
| VerfasserIn |
Mar Alonso, Dylan Ingman, Scott Alexander, José Barrancos, Fátima Rodriguez, Gladys Melián, Nemesio M. Pérez |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128535
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| Publikation (Nr.) |
 EGU/EGU2016-8532.pdf |
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| Zusammenfassung |
| Tenerife is the largest of the Canary Islands and, together with Gran Canaria Island, is the
only one with a central volcanic complex that started to grow at about 3.5 Ma. Nowadays the
central complex is formed by Las Cañadas caldera, a volcanic depression measuring 16×9
km that resulted from multiple vertical collapses and was partially filled by post-caldera
volcanic products. Up to 297 mafic monogenetic cones have been recognized on
Tenerife, and they represent the most common eruptive activity occurring on the
island during the last 1 Ma (Dóniz et al., 2008). Most of the monogenetic cones are
aligned following a triple junction-shaped rift system, as result of inflation produced
by the concentration of emission vents and dykes in bands at 120o to one another
as a result of minimum stress fracturing of the crust by a mantle upwelling. The
main structural characteristic of the southern volcanic rift (N-S) of the island is an
apparent absence of a distinct ridge, and a fan shaped distribution of monogenetic
cones. Four main volcanic successions in the southern volcanic rift zone of Tenerife,
temporally separated by longer periods (∼70 – 250 ka) without volcanic activity, have
been identified (Kröchert and Buchner, 2008). Since there are currently no visible
gas emissions at the N-S rift, diffuse degassing surveys have become an important
geochemical tool for the surveillance of this volcanic system. We report here the last
results of diffuse CO2 efflux survey at the N-S rift of Tenerife, performed using the
accumulation chamber method in the summer period of 2015. The objectives of
the surveys were: (i) to constrain the total CO2 output from the studied area and
(ii) to evaluate occasional CO2 efflux surveys as a volcanic surveillance tool for
the N-S rift of Tenerife. Soil CO2 efflux values ranged from non-detectable up to
31.7 g m−2 d−1. A spatial distribution map, constructed following the sequential
Gaussian simulation (sGs) procedure, did not show an apparent relation between
higher diffuse CO2 emission values and the main N-S axis of the rift. The total
CO2 output released to the atmosphere in a diffuse way has been estimated at 707
t d−1, which represents a value three times higher than the average of the three
studies conducted previously. This observed increase suggests the occurrence of
an episodic enhanced magmatic (endogenous) contribution. This also confirms
the need of periodic diffuse emission surveys in the area as a powerful volcanic
surveillance tool, mainly in volcanic systems where visible gas emanations are
absent.
References:
Dóniz et al., 2008. J. Volcanol. Geotherm. Res. 173, 185.
Kröchert and Buchner, 2008. Geol. Mag. 146, 161. |
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