Pegmatite-like Magnetite-Apatite Deposits of Northern Chile: A Place in the Evolution of Immiscible Iron Oxide Melts?

Apatite from "Kiruna-type" magnetite-apatite deposits of the northern Chilean Iron belt contain abundant melt, gas and liquid-rich inclusions. The study of these inclusions confirms the existence of an immiscible iron oxide-apatite melt that separated from a parental silicate-rich primitive magma. Mineralization at the Carmen de Fierro and Fresia mines shares many features typical of magmatic, pegmatitic and hydrothermal deposits, with most of the magnetite apatite ore being interpreted as magmatic-pegmatitic in origin and reflecting a magmatic-hydrothermal transition in water-saturated conditions. Later hydrothermal fluids, also trapped in apatite crystals, reveal a complex and large-scale brine circulation probably responsible for the formation of neighbouring hematite-magnetite and actinolite-apatite-rich veins.