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| Titel |
Carbon-isotope investigation in fluid inclusions of ultramafic xenoliths from Hyblean Plateau (Sicily, Italy): a signature influenced by mantle heterogeneity. |
| VerfasserIn |
Alessandra Correale, Antonio Paonita, Andrea Rizzo, Fausto Grassa, Mauro Martelli |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250114461
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| Publikation (Nr.) |
 EGU/EGU2015-14810.pdf |
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| Zusammenfassung |
| The understanding of the upper mantle has improved greatly in recent decades thanks to studies of mantle xenoliths and the Hyblean area (Sicily, Italy) ) is one of the rare European volcanic regions where mantle xenoliths outcrop. The xenoliths from this area were studied in many aspects but the isotope carbon marker has not been investigated previously. We measured the carbon isotope signature of the mantle source beneath the Hyblean Plateau by studying the CO2 content entrapped in fluid inclusions from ultramafic xenoliths carried out to surface by some diatreme-related deposits of Miocene age.
The δ13CCO2 measured in the present work (ranging between -4‰ and -2‰) was combined with the noble gases results of the same samples from our previous study. In order to investigate the influence of degassing process on the isotope geochemistry of the carbon, we performed quantitative analyses of the magmatic degassing in the case of δ13CCO2, He/Ar and Ar/CO2 ratios and we put in relation the obtained variability. The results highlighted that degassing processes influence sensibly the He/Ar and Ar/CO2 ratios but not the δ13CCO2 that seems controlled mainly by the extent of contamination of the peridotite by sedimentary and organic carbon. Mass-balance calculations evidenced that the Hyblean peridotite source is mainly contaminated by carbonate crustal term, being carbonate and organic matter characterized by a ratio within the range 5:1 and 7:2.
Instead, mixing processes mainly affect the variable compositional CO2/3He and 3He/4He ratios, ranging between 1.21x109-9x1010 and 7.2-7.6 Ra respectively. More in detail these mixing processes would be triggered by metasomatic intrusions as veins of MORB-type pyroxenitic melts in the peridotite matrix contaminated by crustal fluids probably inherited from a fossil subduction. |
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