PETROGRAPHIC EVIDENCES FOR THE ORIGIN OF IRON IN IOCG IRON DEPOSITS OF KUH-E-FARYADOON AND KOULI-KOSH, SOUTHEAST CENTRAL IRAN

Kuh-E-Faryadoon and Kouli Kosh iron deposits are hosted by regional metamorphic rocks of Sanandaj-Sirjan zone around Deh-Bid area. Plugs and domes of acid rocks protrude these metamorphic rocks. A mylonitization event is super imposed on acid rock and metamorphic complexes. Field, petrological and geochemical studies have shown that (1) Iron mineralization have occurred during mylonitization in N45W shear zones. (2) Mineralization have many characteric pecularities of IOCG hydrothermal deposits. (3) Mylonitization is super imposed on regional metamorphism therefore early paragenesis of regional metamorphism are destabilized and new paragenesis are formed. (4) Iron is released through destabilization of biotite, clinopyroxene, epidote, ilmenite and titanomagnetite of mafic metamorphic rock (mainly greenschists) and acid rocks during mylonitization event. Petrographic evidences and relevant reaction are presented and discussed. (5) Iron is mainly and preferentially released from greenschists. (6) Transport of iron by carbonile complexes are proposed based on direct evidence of Co2 rich solutions during mylonitization.