Phase relations and reaction histories of chloritoid-free and chloritoid-bearing metapelites from the Mahneshan area, NW Iran

Mineral assemblages, reaction textures and mineral composition of the metapelitic rocks from the Mahneshan area in NW Iran are studied to reconstruct the reaction history of the rocks. The phase relation on the real mineral chemistry AFM, AFMn compatibility diagrams and mineral isograds in chloritoid-free and chloritoid-bearing metapelites of Mahneshan Complex were studied in order to determine the reaction history. The main minerals in the graphitic metapelites (chloritoid-free schist) of the Bolandparchin are garnet, staurolite, andalusite, kyanite, fibrolite, biotite, muscovite and quartz. The isograds are typical Barrovian. Chloritoid-bearing metapelites of the area contain the minerals garnet, staurolite, chlorite, muscovite, chloritoid and quartz. The isograds are not compatible with Barrovian type, but reflect the first appearance of chloritoid in the aluminous bulk compositions. Phase relations on the AFM and AFMn compatibility diagram are used to find the metamorphic reactions in both chloritoid-bearing and chloritoid-free rocks.