The study of chemical composition and evolution of minerals during various metamorphic events in the Hamadan region

Metamorphic rocks of the Hamadan region have experienced regional and also contact metamorphism (due to intrusion of gabbro, diorite and granitic bodies), therefore, their mineral assemblages have formed in multiple stages. Evidence of regional metamorphism (M) and contact metamorphisms at the contact of gabbros (M’1) and porphyroid granites (M’2) are separatable, hower At the contact of hololeucocratic granites a very local contact metamorphism (M’3) have occurred (from a few decimeter up to a few meters, due to small size of these bodies). Minerals such as micas, garnet, staurolite, cordierite, andalusite, kyanite and sillimanite are usually produced by several reactions, and participated in other reactions to form other minerals. The relationship between mineral growth to deformational events have been found at several stages (i.e. pre-tectonic, syn-tectonic and post-tectonic minerals are common in metamorphic rocks of the region.) Pegmatites and silicic veins have played essential role in some metamorphic reactions as sources for heat and fluids, so that some metamorphic minerals are common near these veins and disappear far from the veins. Considering observed mineral assemblages in metamorphic rocks of the region, regional metamorphism can be correlated with low to moderate P/high T Buchan type metamorphism. In final stages of metamorphism, high T minerals such as cordierite experienced retrograde reactions or pseudomorphed and higher pressure minerals such as kyanite have been more stable.