Geological position and mineral composition of kyanite amphibolites of the Chupinskiy paragneiss belt (Belomorian province of Eastern Fennoscandia)

The Lyagkomina occurrence of kyanite amphibolites (the Belomorian Province the Fennoscandian Shield) is confined to an amphibolite boudin among kyanite-garnet-biotite and garnet-biotite gneisses Chupa Sequence. main rock types at are meso- melanocratic garnet-kyanite with large (more than 1 cm in length) kyanite-garnet small kyanite. There also leucocratic garnet-biotite-amphibole-plagioclase rocks kyanite, epidote-staurolite-amphibole rocks, zoisite plagioclasites staurolite country around were metasomatically altered: quartz disappears gneisses, amphibole appears gneisses. Calcic amphiboles represented by high-alumina tschermakite; biotite — intermediate-alumina phlogopite; garnet belongs pyrope-almandine series a high grossular content. Plagioclases have intermediate basic composition. Intermediate plagioclases common without rims, while found amphibolites. Many characterized reaction structures, representing change mineral assemblages. Metasomatic zoning has been reconstructed regular sequence assemblages: Hbl + Grt Pl Qtz ± Bt (garnet amphibolite) → Ky St Czo Bt. In described series, alumina content increases Mg rock-forming minerals decreases, desilication occurs. was formed during metamorphism as result between initial fluid flow shear zone (i. e., synmetamorphic metasomatism). Petrological isotope data indicate that genetically related occurrences corundum-bearing Shield.