Role of Cambrian evaporitic fluids in geochemistry and genesis of Nord Anomaly iron ore deposit, North Bafq(Central Iran

Nord Anomaly deposit is an iron ore deposit in Bafq district. It contains 250 Mt iron ore with average grade of Fe=28 %. The host rocks of the mineralization in Nord Anomaly deposit are granitic and microgranitic rocks with probably Early Paleozoic age. Petrographic investigations reveal that sodic and calcic alterations are related to iron mineralization. Other alterations such as silisic, chloritic, epidotic and sericitic alterations are insignificant and post date the iron mineralization. Sodic and calcic alterations are characterized by formation of chessboard albite and actinolite –termolite respectively. Widespread sodic and calcic alterations are contemporaneous with the feldspar-magnetite and magnetite-amphibole ore respectively. Magnetite–amphibole ore is high grade and low tonage while magnetite–feldspar ore is low grade and high tonage. Geochemical studies show that alkaline cations (Na, K) concentration were increased and immobile elements (Fe, V, Ni) decreased during sodic alteration.