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| Titel |
Cr diffusion in MgAl2O4 synthetic spinels: preliminary results |
| VerfasserIn |
C. Freda, B. Celata, G. Andreozzi, C. Perinelli, V. Misiti |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063214
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| Zusammenfassung |
| Chromian spinel is an accessory phase common in crustal and mantle rocks, including
peridotites, gabbros and basalts. Spinel, it has been identified as one of the most
effective, sensible, and versatile petrogenetic indicator in mafic and ultramafic rock
systems due to the strict interdependence between its physico-chemical properties
(chemical composition, cation configuration etc.) and genetic conditions (temperature,
pressure, and chemical characteristics of the system). In particular, studies on intra- and
inter-crystalline Mg-Fe2+, Cr-Al exchange demonstrated the close relationship
between spinel composition and both degree of partial melting and equilibrium
temperature of spinel-peridotites. Moreover, studies focused on the chemical zoning of
Mg-Fe2+ and/or Cr-Al components in spinel have been used, combined with a
diffusion model, to provide quantitative information on peridotites and gabbros
pressure-temperature paths and on deformation mechanisms. Although these potentials, most
of the experimental studies have been performed on spinels hosting a limited content
of divalent iron (sensu stricto, MgAl2O4), whereas the scarce studies on Cr-Al
inter-diffusion coefficient have been performed at 3-7 GPa as pressure boundary
condition.
In order to contribute to the understanding of processes occurring in the lithospheric mantle,
we have initiated an experimental research project aiming at determining the Cr-Al
inter-diffusion in spinel at 2 GPa pressure and temperature ranging from 1100 to 1250 °C.
The experiments were performed in a end-loaded piston cylinder by using a 19 mm assembly
and graphite-Pt double capsules. As starting materials we used synthetic Mg-Al spinel
(200-300Â μm in size) and Cr2O3 powder. Microanalyses of experimental charge were
performed on polished carbon-coated mounts by electronic microprobe. Line elemental
analyses were made perpendicular to the contact surface between Cr2O3 powder and spinel,
at interval of 2 μm. By processing these preliminary data, we have estimated a diffusion
coefficient of chromium (D) of 7.6-
10-15 m2s-1. |
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