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Dave,

        I totally agree - I do not consider Grt+Cpx+Pl definitive of the granulite facies; where I have that assemblage in amphibolitic rocks, without nearby 2-px-bearing mafic rocks, I use the amphibolite-facies pigeon hole.  Of course, this assemblage does occur in the granulite facies as well [~higher bulk Ca]. FWIW...

At 12:13 AM 11/2/2001, David Pattison wrote:
>I'd be careful about this. Grt+Cpx+Pl is the high-P equivalent of Opx+Cpx+Pl, the latter which everyone agrees is granulite. So Grt+Cpx+Pl is certainly characteristic of high-P granulites, but is it definitive? There is quite a division on this point, seemingly depending on perspective. There are a few unambiguous amphibolite-grade occurrences of Grt+Cpx+Pl, but these seem to be less common than granulite grade occurrences. The Grt+Cpx-forming reaction from Hbl+PlQtz evidently is sufficiently multivariant that it occurs over quite a range of temperature, sufficient to span the amphibolite-granulite transition. So to me, the answer is: Grt+Cpx+Pl is characteristic but not definitive of granulite. 



Jim Eckert
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