Melting of amphibole-bearing wehrlites: an experimental study on the origin of ultra-calcic nepheline-normative melts. (Articolo in rivista)

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  • Melting of amphibole-bearing wehrlites: an experimental study on the origin of ultra-calcic nepheline-normative melts. (Articolo in rivista) (literal)
Anno
  • 2006-01-01T00:00:00+01:00 (literal)
Alternative label
  • Medard E.; Schmidt M.W.; Schiano P.; Ottolini L. (2006)
    Melting of amphibole-bearing wehrlites: an experimental study on the origin of ultra-calcic nepheline-normative melts.
    in Journal of petrology (Print); Oxford University Press, Oxford (Regno Unito)
    (literal)
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  • Medard E.; Schmidt M.W.; Schiano P.; Ottolini L. (literal)
Pagina inizio
  • 481 (literal)
Pagina fine
  • 504 (literal)
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  • 47 (literal)
Rivista
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  • 3 (literal)
Note
  • ISI Web of Science (WOS) (literal)
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  • Medard E. 1); Schmidt M.W. 2); Schiano P. 1); Ottolini L. 3). 1) Univ Clermont Ferrand, CNRS, Lab Magmas & Volcans, F-63038 Clermont Ferrand, France; 2) ETH, Inst Mineral & Petrographie, CH-8092 Zurich, Switzerland; 3) CNR, Ist Geosci & Georisorse, Sez Pavia, I-27100 Pavia, Italy; (literal)
Titolo
  • Melting of amphibole-bearing wehrlites: an experimental study on the origin of ultra-calcic nepheline-normative melts. (literal)
Abstract
  • Olivine + clinopyroxene ± amphibole cumulates have been widely documented in island arc settings and may constitute a significant portion of the lowermost arc crust. Because of the low melting temperature of amphibole (~1100°C), such cumulates could melt during intrusion of primary mantle magmas. We have experimentally (piston-cylinder, 0·5-1·0 GPa, 1200-1350°C, Pt-graphite capsules) investigated the melting behaviour of a model amphibole-olivine-clinopyroxene rock, to assess the possible role of such cumulates in island arc magma genesis. Initial melts are controlled by pargasitic amphibole breakdown, are strongly nepheline-normative and are Al2O3-rich. With increasing melt fraction (T > 1190°C at 1·0 GPa), the melts become ultra-calcic while remaining strongly nepheline-normative, and are saturated with olivine and clinopyroxene. The experimental melts have strong compositional similarities to natural nepheline-normative ultra-calcic melt inclusions and lavas exclusively found in arc settings. The experimentally derived phase relations show that such natural melt compositions originate by melting according to the reaction amphibole + clinopyroxene = melt + olivine in the arc crust. Pargasitic amphibole is the key phase in this process, as it lowers melting temperatures and imposes the nepheline-normative signature. Ultra-calcic nepheline-normative melt inclusions are tracers of magma-rock interaction (assimilative recycling) in the arc crust. (literal)
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