Eric and others,
apologies if my message is out of the topic of the discussion, I did not
fellow from the start, just from Eric's email - for interest I would like to
add one info about cor-magn-hercynite: I reported the same as what Eric
mentioned below (corundum in magnetite-hercynite, with sillimanite and
quartz) bearing rocks in Namaqualand (South Africa) (see Mouri et al,
Mineralogical Magazine Vol., 67(5), 1015-1021) where spinel and quartz are
observed in contact indicating UHT conditions, I did some calculation of T
where corundum coexist with magnetite-spinel (see Mouri et al., 2004,
JOURNAL OF MINERALOGICAL AND PETROLOGICAL SCIENCES SPECIAL ISSUE ON
Ultrahigh temperature metamorphism and deep crustal processes). It seems
that when corundum is present with hercynite - magnetite - it might indicate
UHT conditions - where melting and migmatite forming processes are possible
depending on the source composition of course (?).
Cheers
hassina
----------------------------------
Dr Hassina MOURI
Acting Head of Department
Department of Geology
University of Pretoria
Pretoria 0002
Republic of South Africa
Tel (office): (+27 12) 420 24 56
Fax: (+27 12) 362 52 19
Cell: 083 417 5759
E-mail: [log in to unmask]
http://www.up.ac.za/academic/geol/pers/Hassina.html
"The important thing is not to stop questioning." - Albert Einstein
> 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
>
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