Joe,
Solid solution of excess Al2O3 in spinel is equivalent to a
maghemite-type or "beta corundum" substitution, which is less dense
than a corundum-spinel mixture. One would therefore expect that the
solid solution would be reduced at high pressure, and the spinel in
these xenoliths may have minimal vacancies even in equilibrium with
corundum.
eric
>At 9:02 PM +0530 3/20/03, Santanu Kumar Bhowmik wrote:
>>Dear All,
>>Would anybody know reference of works, which described exsolutions of
>>spinel in corundum in aluminous granulites and related rocks? Many thanks
>>in advance.
>>Best regards,
>>Santanu Kumar Bhowmik
>
>Santanu,
>
> I don't know if the corganites and corgaspinites described by
>Mazzone and Haggerty possess exsolution textures, but the the
>assemblage (garnetąspinelącorundum) and bulk composition sounds like
>a match
>
>The reference is
>
>Mazzone, P. and Haggerty, S.E. (1989) Corganites and corgaspinites:
>two new types of aluminous xenoliths form the Jagersfontein
>kimberlite pipe. Kimberlites and Related Rocks, Part 2. Geological
>Society of Australia Special Publication, 14, pp. 795-808.
>
>Joe
>
>____________________________________________________________________________
>Dr. Joseph Pyle
>Department of Earth and Environmental Sciences
>Rensselaer Polytechnic Institute - 110 8th St., Troy, NY 12180
>phone: (518) 276-4899
>fax: (518) 276-6680
>email: [log in to unmask]
>web page: http://www.rpi.edu/~pylej
>____________________________________________________________________________
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