Dear all,
should we really bother? Personally, I hate
nomenclature and avoid it as much as possible
even in my lectures. Choose the name that you
like (preferably simple, e.g. garnet amphibolite)
for the purpose of a talk or a paper and explain
what you mean by this in this specific context,
that's all.
In any case, I believe that interpretative names
(amphibolitised eclogite, hornblendized
blueschist etc.) should be avoided, precisely
because they depend on your interpretation (that
may be wrong). Names listing all the minerals,
although obeying some rules, are just ridiculous
- and some accessory phases could complain for
not having been listed... ;-)
cheers,
Pavel
--
>Dear Jarek,
>
>You are indeed correct. There are minor relics
>of Gln within Hbl, suggesting that the prograde
>path passed through the epidote blueschist. But
>at the metamorphic peak, Gln is completely
>absent, and the main amphibole is Hbl. So, the
>problem of nomenclature remains.
>
>Thanks.
>
>Santanu
>
>----- Original Message -----
>From: "Jarek Majka" <[log in to unmask]>
>To: "Metamorphic Studies Group"
><[log in to unmask]>,
>[log in to unmask]
>Sent: Wednesday, December 17, 2014 9:22:32 PM
>Subject: Re: [geo-metamorphism] Rock Nomenclature
>
>Santanu,
>
>It seems to me like a former blueschist, which has undergone some
>heating. Have you searched carefully for a proper Na-amphibole relicts
>in your hornblende?
>
>Best,
>Jarek
>
>
>
>> Dear Colleagues,
>>
>> I am seeking your suggestions on the
>>nomenclature of a metamorphic rock with the
>>assemblage
>>garnet+hornblende+epidote+phengite+rutile+quartz.
>>This assemblage which became stable during peak
>>metamorphism yielded P-T estimate of ~ 15-16
>>kbar,~ 590-610 °C. If this assemblage is
>>evaluated with metamorphic rocks that are
>>related to metamorphism during subduction
>>initiation, the closest rock name that comes to
>>my mind is garnetiferous amphibolite. However,
>>in the strictest sense, the rock, in the
>>absence of plagioclase cannot be an
>>amphibolite, if we use amphibolite in facies
>>sense. At the same time, the estimated P-T
>>range lies in the eclogite facies, also
>>supported in part by complete elimination of
>>plagioclase. However, with omphacitic
>>clinopyroxene being absent, the rock is also
>>not an eclogite in the strictest sense. One
>>additional information in this regard is that
>>Na in the protolith is completely partitioned
>>in Hbl, which shows substantial presence of Na
>>in the M4 site, apart from its general
>>occurrence in the A site.
>>
>> Your comments and observations are welcome.
>>
>> With regards,
>>
>> Santanu
>> -------------------------------------------------------
>> Dr. Santanu Kumar Bhowmik
>> Professor
>> Department of Geology & Geophysics
>> Indian Institute of Technology
>> Kharagpur-721 302
>> India
>> Mobile:+919434041791
>> Telephone:+91-3222-283390(O), 283391, 279766(R)
>
>--
>Jaroslaw Majka Ph.D., Docent
>Researcher and EMP Lab Manager
>Department of Earth Sciences
>Uppsala University
>Villavägen 16
>SE-752 36 Uppsala, Sweden
>Fax: (+46) 18-501 110
>Mobile: (+46) 702823330
>Email: [log in to unmask]
>http://jaroslawmajka.com/
--
Pavel PITRA
Géosciences Rennes email: [log in to unmask]
Université Rennes 1 tel: (++33) 2.23.23.65.06
Campus de Beaulieu - Bat. 15 fax: (++33) 2.23.23.67.80
F - 35 042 RENNES CEDEX
FRANCE http://www.geosciences.univ-rennes1.fr/
http://www.geosciences.univ-rennes1.fr/spip.php?article67
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