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| Titel |
Magmatic versus sedimentary 87Sr/86Sr signature in groundwater circulating in a basaltic volcanic systems: Mt. Etna |
| VerfasserIn |
Marcello Liotta, Walter D'Alessandro, Ilenia Arienzo, Manfredi Longo |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143595
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| Publikation (Nr.) |
 EGU/EGU2017-7330.pdf |
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| Zusammenfassung |
| Volcanoes can host large aquifers and thereby represent important water resources.
Groundwater interacting with volcanics dissolves volcanogenic elements that subsequently
flow through the aquifers. Volcanic systems often overlie a crustal basement. At Mt. Etna,
groundwater mainly circulates in the permeable volcanics that overlie impermeable terrains
composed by allochthonous series of flysch and postorogenic clayey sediments. The use of Sr
isotopes is a well-established approach for tracing fluids in the crust. Since the 87Sr/86Sr ratio
of the volcanics at Mt. Etna exhibits a range that differs significantly from that of the
sedimentary basement, the Sr-isotope composition provides a useful tool for evaluating the
interaction between shallow groundwater circulating in the volcanics and deep brines
circulating in the sedimentary basement. Nowadays it is well known that the main
aquifer on Mt. Etna is hosted in the volcanics. Samples from 14 sites were collected
and analyzed for their chemical composition and Sr-isotope ratios. While the most
common approach of coupling 87Sr/86Sr ratios with the concentration of dissolved Sr
is not effective in distinguishing between the deep brine and possible seawater
contributions, we suggest that the Sr/Cl ratio is a useful complementary parameter that
needs to be considered when attempting to clearly identify the Sr sources. The
obtained data indicate that the Sr-isotope signature of groundwater is determined by
the volcanics of the aquifer. The volcanic isotopic signature is modified by very
small amounts of brines (<1%), characterized by a high concentration of Sr and a
87Sr/86Sr ratio typical of sedimentary environments, but only at sites where the
groundwater circulates almost in contact with the sedimentary basement. The proposed
approach is potentially very effective for tracing the circulation of groundwater not
only at Mt. Etna but also at volcanic edifices that overlie a bedrock with different
87Sr/86Sr ratios as well as at volcanic islands where freshwater overlies seawater. |
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