Abstract:
The iron-titanium (Fe-Ti) oxide ore bodies occur as elongated bands within the gabbro-anorthosite suite of rocks of the Mesoarchean Nuasahi ultramafic-mafic complex. The ore consists mostly of titanomagnetite and ilmenite with minor amounts of hematite, spinel and ulvospinel. Goethite and martite are present as secondary minerals. The titanomagnetite grains display various intergrowth textures such as crystallographic intergrowth, granular intergrowth, graphic intergrowth, resulting from exsolution and oxidation above and below the magnetite-ulvospinel solvus. Bulk rock data shows that the ore contains 0.2 to 0.8 wt% V(2)O(3) and 7.2 to 19.4 wt% TiO(2). It is strikingly low in silica (0.4 to 2.8 wt%) indicating near absence of silicate minerals. The bulk rock chemistry in conjunction with mineralogical findings indicate that the ore minerals have undergone alteration resulting in development of martite, goethite and lepidocrocite. Ilmenite-magnetite geothermo-barometry data indicate that the mineralogical assemblage and textural characters have developed within a temperature range of 575 to 925 degrees C and oxygen fugacity of 10(-11) to 10(-22.5). The iron-titanium oxide ore bodies are genetically related to the gabbro-anorthosite suite of rocks. The present geometrical disposition of the ore bodies is due to residual liquid injection of the filter pressed - concentrated mass. The predominantly monomineralic nature of the ore body may be due to post cumulus sintering or annealing process. The utilization potential of these ores has been tested in producing a titania-rich slag (TiO(2)-88%) from which titanium can be recovered easily and for producing Fe-Ti-C composite (Ti-83%), a high value product.