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)
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