Mineralogy and geochemistry of Fe-Ti oxide ores from the Don Dieguito massif-type anorthosite suite, Sierra Nevada de Santa Marta, Colombia

Fe-Ti oxide ores are commonly asso-ciated with Proterozoic massif-type anorthosite bodies emplaced during the Grenville orogen), (similar to 1.2-1.0 Ga). Some of these anorthositic bodies occur in the northernmost part of the Santa Marta Massif, Colombia. They locally contain crosscutting Fe-Ti(-V) ore bodies between the El Hierro creek and the Don Dieguito river. We have distinguished two types of Fe-Ti(-V) ores: i) oxide-apatite norite (line grained ilmenite and magnetite disseminated in an assemblage of apatite, amphibole, chlorite, rutile and sericitized plagioclase) and ii) banded nelsonite (coarser grained ilmenite, magnetite and apatite distributed in hands, with minor baddeleyite, srilankite and hiigbomite). Ihnenite in the two ore types display distinct hematite exsolution features: a) needle-like in the oxide-apatite norite ore; and b) two generations of exsolutions in the banded ore. Magnetite shows similar Ti and V contents in both ore types (0.4 wt % TiO2 and 0.5 wt % V2O5 on average in the oxide-apatite norite ore, 0.5 wt TiO2, and 0.4 wt V2O3 in the banded ore), whereas ilmenite has higher hematite., pyrophanite and geikielite components in the handed ore. The ores might have formed from the combination of fractional crystallization and magma mixing, with exsolution occurring probably at 575-600 degrees C. This first detailed mineralogical and textural study of Fe-Ti(-V) oxide ores in anort.hosite massifs from Colombia suggests that the Santa Marta Massif is an interesting target for hiture research.