PROCESS MINERALOGICAL STUDIES ON IRON ORE OF OJAT-ABAD MINE IN SEMNAN

Ojat-Abad Iron mine is located in northern Iran, about 73 km east of Semnan, in the iron metallogenic belt of Semnan Province. Hematite is the main ore mineralization in the studied area, with 4 main forms of Fe mineralization; hard and compact hematite with magnetite, fine hematite, concretion hematite inside fine hematite matrix, and ocher. Limestone and sandstone adjacent to andesite and basalt-andesite are the host rock of the Fe mineralization. Ca and Mg carbonates, quartz, and feldspar are the most important gangue minerals. Carbonate minerals are in the form of cement in hematitic concretion, calcite veins and also as limestone and limestone-dolostone host rock. Quartz and feldspar are associated with ocher hematite and are also the main rock-forming minerals in sandstone host rock. Based on the chemical analysis, hard hematite has the highest content of Fe2O3 and ocher has the highest content of SiO2.The sum of P2O5, MnO and SO3 are less than 1 % in the ore minerals. Arsenic concentration was determined up to 1200 ppm in the hematite by EPMA.