Ah, nomenclature...
Since I guess I started this, first I should point out that in no way did I intend to 'accuse' Anthi of misusing terms, I just thought some potential for ambiguity might exist; I fully realize Anthi did not refer to the rocks as being amphibolite *facies*. Judging by subsequent responses, I may actually have been correct... I responded because I have dealt with this terminology problem myself, so just wanted to add a point of clarification; frankly, I really think the ensuing discussion is valuable. As everyone on here certainly understands, although the rocks are 'amphibolites', the *assemblage* may not indicate the amphibolite *facies*. Thanks very much for your information, Anthi and everyone else; this kind of discussion seems useful toward achieving some agreement on how to approach the issue of separating the rock-type terminology from the metamorphic assemblage/facies terminology.
Although this may be something of a cop out, in discussing 'amphibolites' [amphibole+plag dominated rocks] that contain the diagnostic granulite-facies assemblage [cpx+opx], in many cases I default to '2-pyroxene amphibolitic rocks', in an attempt to circumvent the possible misimpression that the assemblages are amphibolite facies, rather than granulite facies. Though it is a bit awkward, I'm not certain I've seen a term I prefer [including here]. 'Metabasites' I sometimes use in verbal discussion, but that leaves out other textural connotations that come along with 'amphibolite' [e.g., vs. metagabbro]. My only objection to 'pyroxene amphibolite' might be that it does not specify the diagnostic TWO-pyroxene assemblage. I have no problem with, and sometimes use, '2-pyroxene amphibolite', though [so far] not in publications. Finally, to be honest, in the field I just call them amphibolites.
Hopefully I have not confused anything or anyone further. Sorry for opening the can o' worms, but thanks again for the lively exchange.
At 11:17 AM 11/2/2001, Tomas Feininger wrote:
> 2.x.'01
>
>Tom, Eric and others,
>
> What's wrong with the term 'pyroxene amphibolite'? I've used it in publications and never been called to task...
>
> Tomas Feininger
> Geologist & Prof
> Université Laval.
Best Regards,
JIM ECKERT
<[log in to unmask]>
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James O. Eckert, Jr., Ph.D
Department of Geology and Geophysics, Yale University
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