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.