Metabasite from the Variscan belt in NE Sardinia, Italy: within-plate OIB-like melts with very high Sr and low Nd isotope ratios (Articolo in rivista)

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  • Metabasite from the Variscan belt in NE Sardinia, Italy: within-plate OIB-like melts with very high Sr and low Nd isotope ratios (Articolo in rivista) (literal)
Anno
  • 2010-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1127/0935-1221/2010/0022-2042 (literal)
Alternative label
  • Cruciani G. (1); Dini A. (2); Franceschelli M. (1); Puxeddu M. (2); Utzeri D. (1) (2010)
    Metabasite from the Variscan belt in NE Sardinia, Italy: within-plate OIB-like melts with very high Sr and low Nd isotope ratios
    in European journal of mineralogy (Print); E SCHWEIZERBARTSCHE VERLAGS, Stuttgart (Germania)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Cruciani G. (1); Dini A. (2); Franceschelli M. (1); Puxeddu M. (2); Utzeri D. (1) (literal)
Pagina inizio
  • 509 (literal)
Pagina fine
  • 523 (literal)
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  • http://eurjmin.geoscienceworld.org/content/22/4/509.abstract (literal)
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  • 22 (literal)
Rivista
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  • In: European Journal of Mineralogy, vol. 22 (4) pp. 509 - 523. Schweizerbart, 2010. (literal)
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  • 15 (literal)
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  • Scopu (literal)
  • ISI Web of Science (WOS) (literal)
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  • (1) Dipartimento di Scienze della Terra, Università di Cagliari, Italy, (2) Istituto di Geoscienze e Georisorse - CNR, Pisa, Italy (literal)
Titolo
  • Metabasite from the Variscan belt in NE Sardinia, Italy: within-plate OIB-like melts with very high Sr and low Nd isotope ratios (literal)
Abstract
  • A metabasite lens with eclogite-facies relics discovered within high-grade gneisses, at Punta Orvili (Posada) in NE Sardinia, has proven to be the first example of within-plate basalt among the eclogite-derived, tholeiitic metabasites from the Variscan belt in Sardinia. The composition of the Punta Orvili metabasite is unusual: SiO(2) < 47.6 wt%, Al(2)O(3) < 9.6 wt%, MgO >= 13 wt%, Fe(2)O(3tot) > 13 wt%, Cr > 550 ppm, Ni > 270 ppm, Mg # 68-70. Detailed investigation of the major and trace element content rules out any significant geochemical modification of the protolith by alteration and/or metamorphic processes. Normative contents of mafic minerals up to 55-79 wt%, very small amounts of Al(2)O(3) and Na(2)O and very high concentrations of MgO, Cr and Ni suggest a protolith of picritic nature. The steeply sloping REE patterns, with La(N)/Yb(N) = 13.0-17.3, suggest low-degree partial melting and the presence of garnet, as retention phase of HREE in the mantle source. Enrichment factors are 60-180 times higher for LREE, 30-60 times for MREE, 10-20 times for HREE. The primitive manntle-normalized trace element abundance patterns of the Punta Orvili metabasite show enrichment in Ba, Th, Nb, La, Ce, compared to eclogite-derived metabasites. Values of La/Nb, La//Ta, Ce/Nb, Th/Nb, Sm/Yb, Ce/Sm, Th/Y, Nb/Y, Th/Yb and Ta/Yb differ significantly from those of average crust, upper, lower and mid-crust, indicating an OIB-like source. Two values of (87)Sr/(86)Sr((i)) were obtained around 0.709 with epsilon(Sri) =+69-71. The corresponding values of the (143)Nd/(144)Nd((i)) are about 0.51197 with epsilon(Ndi) similar to -1.50 assuming an age of 460 Ma, i.e. the mean age of Sardinian eclogite. Isotope and geochemical data suggest that the Punta Orvili protolith was generated by interaction of OIB-like melts with an enriched sub-continental lithospheric mantle, similar in composition to Group II kimberlites and/or to their garnet peridotite xenoliths. (literal)
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