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; FFFF,0000,0000Note: -5987371
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