Amphibolite-hosted Fe-Ti oxide mineralization of the Mitrashinci deposit, Eastern Macedonia

The Mitrashinci deposit in Eastern Macedonia represents a unique type of metamorphosed Fe-Ti deposits. Fe-Ti oxide mineralization was identified in amphibolites from the metamorphic complex of the Serbo-Macedonian massif, which comprise two different stratigraphic horizons striking NW-SE. At Mitrashinci, Fe-Ti oxide mineralization is hosted by deeply buried amphibolites of the second stratigraphic horizon. Two types of amphibolites were recognized, almost barren garnet-biotite and mineralized garnet-cummingtonite. The mineralized zone (varying in thickness from 20 to 300 m) has been traced for 12 km within amphibolite host rocks. Several lens-like ore bodies hosted by garnet-cummingtonite amphibolites striking NW-SE have been intersected by mining operations at Kobilski Rid, Gromadna, Leskovica, Dolga Poljana, and Bliznakov Cukar. The contents of Fe and Ti vary greatly in the ores (13–23% and 4–9.1%, respectively). The ore bodies consist mainly of Fe-Ti oxides, such as magnetite, titanomagnetite, ilmenite, and hematite (martite), and minor pyrite, chalcopyrite, pyrrhotite, rutile, titanite, leucoxene, and goethite. The major ore minerals (ilmenite, titanomagnetite, and magnetite with a minor sulfide phase) were formed during the magmatic phase of ore deposition and were not considerably affected by subsequent polyphase metamorphism.