1 De part ment of Ge ol ogy, Bu-Ali Sina Uni ver sity, Hamedan, Iran Sepahi A. A., Borzoei K., Sa lami S. (2013) Min eral chem is try and thermobarometry of plutonic, meta mor phic and anatectic rocks from the Tueyserkan area (Hamedan, Iran). Geo log i cal Quar terly, 57 (3): 515-526, doi: 10.7306/gq.1108The study area is a part of the NW to SE strik ing Sanandaj-Sirjan meta mor phic belt in west ern Iran. The Alvand Pluton, consist ing of rocks that range in com po si tion from gab bro to gran ite, is the ma jor mag matic rock com plex of this area. Gabbroic rocks in clude ol iv ine gab bro, gab bro norite, norite and gab bro. Rocks around the Alvand Pluton were sub jected to dif fer ent P-T con di tions due to polymetamorphism. Com mon meta mor phic rocks are meta-pelites, but some meta-psammites, meta-basites and meta-car bon ates also oc cur. Slates, phyllites, schists, migmatites and hornfelses are ma jor rock units of meta-pelites in the meta mor phic se quence. Based on min eral chem is try, the high est tem per a ture of crystallisation (1300°C) was de ter mined for the ol iv ine gab bros, and the low est tem per a ture (950°C) was cal cu lated for the hornblende-bear ing gabbros. Clinopyroxene-plagioclase ba rom e try sug gests that pres sures near 5 to 6 kbars pre vailed dur ing the crystallisation of the var i ous mafic rocks. P-T es ti mates yield max i mum tem per a tures of 700-750°C at 5-6 kbars for the high-grade meta morphic rocks from the meta mor phic au re ole around the pluton. These re sults in di cate that the heat re leased from the Alvand Pluton (T = 950-1300°C), which in truded the meta mor phic rocks at mid dle and up per crustal lev els, was suf fi cient to cause par tial melt ing lead ing to for ma tion of the metatexites, diatexites and restite-rich S-type gran ites. Dur ing this pro cess, part of the deep-seated gab bro-dioritic rocks were trans ported to higher crustal lev els by vis cous, en clave-and crys tal-rich gra nitic mag mas of the par tial melt ing zone.