Saturday, October 13, 2012

High aluminous metamorphic rock, Keivy. Al2[SiO4]O phases.

Short post about the thin section of biotite-kyanite carbonaceous schist from Keivy, Kola peninsula, Russia. The rock was invloved in processes of muscovitization, staurolitization, alteration, retrogressive metamorphism etc. I would like to show several pictures of Al2[SiO4]O modifications and high aluminous phases.

Fig. 1. All three Al2[SiO4]O modifications that has been formed due to different processes occured here.  Kyanite as a paramorphose after andalusite, sillimanite as a product of thermal reaction, andalusite as relict in newly formed muscovite aggregate. XPL.

Fig. 2. The same field, PPL.

Fig. 3. Staurolitization. Staurolite replaces kyanite crystal. PPL.

Fig. 4. Fibrous sillimanite aggregate, muscovitization and chloritization of biotite. PPL.
The pictures show complex and multi-step process of metamorphism of highly aluminous metasediments. 

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