Tom,
I do not like the term. It certainly would be confused with the
mineral group "pyribole", which I think was coined by Jim tompson in the
60's. Feldspar of course is not part of the group nor of the name
"pyribolite". What's wrong with metamafite? Pyroclasite is used by some
European workers but to me implies orthoclase is possible too.
eric
Anthi, Jim and others,
> At this juncture, I'd like to put in a plug for the very useful term
>"pyribolite", coined by Asger Berthelsen forty years ago to denote a
>metamafite consisting of pyroxene, amphibole and plagioclase, which it would
>be misleading to call amphibolite. Berthelsen (Meddelelser om Gronland, Bd.
>123, Nr. 1, 1960) defined pyribolite to be a metamafite with an amph:px
>ratio ranging from 66:33 to 33:66 but I personally take the liberty of
>broadening that range to take in the bulk of high-grade mafic rocks that
>cannot in good conscience be termed amphibolites. For metamafites with >50%
>plagioclase, Berthelsen coined the term "pyriclasite".
> I am aware that J.B. Thompson in 1970 took over Johannsen's (1911)
>collective noun for pyroxene and amphibole, "pyribole", and proposed it for
>minerals with combined pyroxene and mica-like structural units but there's
>hardly much room for confusion: anyway Berthelsen preceded Thompson by 10
>years.
> Cheers.
>Tom Frisch
>________________________
>Thomas Frisch
>Geological Survey of Canada
>601 Booth Street
>Ottawa, ON K1A 0E8
>Canada
>E-mail: [log in to unmask]
>
>
>> Jim,
>> There must be some misunderstanding. The rock I am talking about WAS an
>> amphibolite which has undergone contact metamorphism due to a granodiorite
>> intrusion. Contact metamorphism of this amphibolite resulted in the
>> formation of the present cpx-opx-plag 'hornfelses, in which relics of the
>> original amphibolite occur in form of patches.
>> I hope this clarifies what I meant in my previous e-mail.
>>
>> cheers
>> Anthi
>> Dr Anthi Liati
>> Institute of Isotope Geology and Mineral Resources
>> Department of Earth Sciences
>> ETH-Zentrum
>> Sonneggstr. 5, 8092 Zürich
>> Tel. ++41 1 632 6607
>> ++41 1 632 3764 (secretary Mrs. Britt Meyer)
>> Fax ++ 41 1 632 1827
>>
>>
>>
>>
>> At 15:41 01.11.01 -0500, you wrote:
>> >Anthi:
>> >
>> > FWIW, with cpx+opx your assemblage is granulite or
>> pyroxene-hornfels facies, not 'amphibolite'. I agree totally that the
>> rocks still may be 'amphibolite', and I share that use of the terminology
>> for the rock. Just thought this distinction might deserve mention.
>> Everyone stay safe.
>> >
>> >
>> >JIM ECKERT
>> ><[log in to unmask]>
>> >------------------------------------------------------------
>> >James O. Eckert, Jr., Ph.D
>> >Department of Geology and Geophysics, Yale University
>> >------------------------------------------------------------
>> >
>>
>> -----------------------------------------------------------------------
>>
Eric Essene
Professor of Geology
Department of Geological Sciences
2534 C.C. Little Bldg.
425 E. University Ave.
University of Michigan
Ann Arbor MI 48109-1063 USA
fx: 734-763-4690
ph: 734-764-8243
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