Subduction-like fluids in the genesis of Mt. Etna magmas:evidences from boron isotopes and fluid mobile elements (Articolo in rivista)

Type
Label
  • Subduction-like fluids in the genesis of Mt. Etna magmas:evidences from boron isotopes and fluid mobile elements (Articolo in rivista) (literal)
Anno
  • 2001-01-01T00:00:00+01:00 (literal)
Alternative label
  • Tonarini S., Armienti P., D?Orazio M., Innocenti F. (2001)
    Subduction-like fluids in the genesis of Mt. Etna magmas:evidences from boron isotopes and fluid mobile elements
    in Earth and planetary science letters
    (literal)
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  • Tonarini S., Armienti P., D?Orazio M., Innocenti F. (literal)
Pagina inizio
  • 471 (literal)
Pagina fine
  • 483 (literal)
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  • The paper presents new boron isotope data together with trace element contents and Sr, Nd isotopic ratios for pre-historical and historical lavas from Mt. Etna Volcano, Sicily. This volcano is presently one of the most active in the world and it is located in a highly populated area, thus detailed petrological and geochemical studies are not only important on accademic point of view but also for civil defence implications. (literal)
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  • 192 (literal)
Rivista
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  • Impact factor: 2,700 (literal)
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  • Systematic comparison of Sr isotopic equilibrium between whole rocks and pyroxene phenocrysts indicates that three isotopically distinct magma batches fed the volcano during the investigated time span. Moreover, sporadic but well recognizable shallow contamination effects induce lowering of ?11B values accompanied by Sr isotopic disequilibrium between cpx and host rock. This study implies active involvement of a subduction-like fluid component in the genesis of Mt. Etna alkaline magmas. The systematic temporal variations in B and Sr isotopic compositions combined with Nb/fluid mobile element ratios are explained with the addition to the mantle source of between 0.1-1% of fluid released by the nearby subducting Ionian slab. The slab window generated by the differential roll-back of the Ionian slab with respect to the Sicilian continental lithosphere, provides the geodynamic setting in which the passive rise of asthenosphere may induce the partial melting responsible of Mt. Etna magmatism, whereas fluids released by subducting slab imprint a progressive signature of FME enrichment to Etnean lavas. (literal)
Note
  • ISI Web of Science (WOS) (literal)
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  • Tonarini S. : Istituto di Istituto di Geoscienze e Georisorse, CNR, Via Moruzzi 1, I-56127 Pisa – Armienti P., D’Orazio M. and Innocenti F.: Dipartimento di Scienze della Terra, Università di Pisa, via S. Maria 53, Pisa (literal)
Titolo
  • Subduction-like fluids in the genesis of Mt. Etna magmas:evidences from boron isotopes and fluid mobile elements (literal)
Abstract
  • New whole-rock B, Sr, Nd isotope ratios and 87Sr/86Sr on clinopyroxenes have been collected to study the enrichment of fluid-mobile elements (FMEs) observed in Mount Etna volcanics. Etna volcano, one of the most active in the world, is located in an extremely complex tectonic context at the boundary between colliding African and European plates. The analytical work focuses on current (1974-1998) and historic (1851-1971) eruptive activity, including some key prehistoric lavas, in order to interpret the secular shift of its geochemical signature to more alkaline compositions. Boron is used as a tool to unravel the role of fluids in the genesis of magmas, revealing far-reaching consequences, beyond the case study of Mt. Etna. Small variations are observed in ?11B (-3.5 to -8.0‰), 87Sr/86Sr (0.70323-0.70370), and 143Nd/144Nd (0.51293-0.51287). Moreover, temporal evolution to higher ?11B and 87Sr/86Sr, and to lower 143Nd/144Nd, is observed in the current activity, defining a regular trend. Sr isotopic equilibrium between whole-rock and clinopyroxene pairs indicates the successive introduction of three distinct magma types into the Etna plumbing system over time; these are characterized by differing degrees of FME enrichment. In addition, certain lavas exhibit evidence for country rock assimilation, magma-fluid interaction, or magma mixing in the shallow feeding system; at times these processes apparently lowered magmatic ?11B and/or induced Sr isotopic disequilibrium between whole rock and clinopyroxene. The regular increase of ?11B values is correlated with Nb/FME and 87Sr/86Sr ratios; these correlations are consistent with simple mixing between the mantle source and aqueous fluids derived from nearby Ionian slab. The best fit of Mount Etna data is obtained using an enriched-MORB mantle source and a fluid phase with ?11B of about -2‰ and 87Sr/86Sr of 0.708. We argue that the slab-window generated by differential roll-back of subducting Ionian lithosphere (with respect to Sicily) allows the upwelling of asthenosphere from below the subduction system and provides a suitable path of rise for subduction-related fluids. The increasing geochemical signature of fluid mobile elements enrichment to Mt. Etna lavas is considered a consequence of the progressive opening of slab window through time. (literal)
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