All,
We also reported corundum in complex textures with hercynite,
magnetite and hogbomite in sillimanite gneisses. The assemblage may
form during early retrogression by oxidation of a complex high-T spinel
solid solution.
eric
On Dec 10, 2004, at 7:25 AM, Frank Beunk wrote:
> At 10:04 10/12/2004 +0100, you wrote:
>
> Horst and all,
> See also p. 122-123 in Ashworth's 1985 book on Migmatites, referring
> to the contact aureole of the Laramie anorthosite. Apparently,
> corundum can form on the supersolidus as well as the subsolidus side
> of incongruent quartz-free dehydration melting equilibria in
> metapelitic compositions. The textures Kare has shown us made me think
> of such an origin in the first place.
> cheers,
> Frank
>
>
> Dear all,
>
> just to give a different example:
> Corundum may also form by metamorphic reactions at high T in
> low-silica
> sub-domains of felsic granulites. We have found corundum in hercynite
> +
> cordierite pseudomorphs after kyanite (Fig. 2d of Marschall et al.,
> 2003). The rocks were also partially melted during their HT history,
> but formation of corundum is clearly not related to melting or melt
> crystallisation.
>
> cheers,
>
> horst
>
>
> Marschall HR, Kalt A, Hanel M (2003) P-T Evolution of a Variscan Lower
> Crustal Segment: a study of granulites from the Schwarzwald, Germany.
> J
> Petrol 44: 227-253
>
>
> --
> Horst R. Marschall
> Mineralogisches Institut
> Universitaet Heidelberg
> INF 236
> 69120 Heidelberg
> Germany
>
>
>
>
> -------------------------------------
> Frank F. Beunk
> Faculty of Earth and Life Sciences, Vrije Universiteit
> Dept. of Petrology
> De Boelelaan 1085, room F062
> NL-1081 HV Amsterdam, Netherlands
> T +31-20-4447371; Note: -5987371 as per Jan. 1, 2005
> F +31-20-6462457
> E [log in to unmask]
>
>
