IOCG and IOA deposits form the Carajás Mineral Province: Approach from ore-forming processes/ore deposits linking textures with chemical/isotopic compositions.
IOCG, Magnetite, Mineralogy, Geochemistry, Carajás.
The Iron oxide copper-gold IOCG deposits are featured by large volumes of magnetite as the main Fe-oxide, which through textures and chemistry records the origins of ore-forming fluids and multiple overprints. Combined, petrography and geochemical evidence found in magnetite from Jatobá and Jaguar deposits located in the Carajás Mineral Province, show a formation at the early hydrothermal alkali-calcic alteration with features comparable with silician magnetite. The magnetite grains from both deposits forms in the presence of calcic-magnesium silicates with geochemical modelling at >450° C and are typified by Ti-rich trellis lamellae of ilmenite and sub-micrometer inclusions. Besides, these magnetite grains are accompanied by Ni-rich sulphide mineralogy and preserve the same geochemical signature from the early hydrothermal formation to the later low-temperature vein stage, suggesting that the ore in each deposit could be attributable to the evolution of a Ni-bearing fluid that holds the Ca-Fe features of an IOCG system.