The apatite-ilmenite deposit of the Cambrian Sept-Iles layered mafic complex, Quebec.

The gently dipping apatite units, up to 175 m thick, include 107 800 000 t grading 15% apatite and 16% ilmenite. The complex is a circular intrusion, 80 km in diameter, reflecting three major Cambrian magmatic cycles. The first cycle is divided into the Lower Series of unlayered troctolites and the 3 km thick Layered Series of troctolites, olivine gabbros and gabbros, containing more than 15% Fe-Ti oxides and terminating in the 250 m thick Critical Zone that hosts the deposits. The rocks of the 10 m Nelsonite Subzone contain more than 90% Fe-Ti oxides and apatite, the latter exceeding 25 wt%. The 150 m Gabbro-Nelsonite Subzone has more than 50% nelsonite in its lower half, while the proportion of silicates increases upwards. Fractionation of the nelsonites could have been favoured by enrichment of the parent magmas in Fe, Ti and P before their final emplacement. Production is projected at 4 000 000 t/a by open pit, yielding 600 000 t/a apatite and 330 000 t/a ilmenite concentrates.
The gently dipping apatite units, up to 175 m thick, include 107 800 000 t grading 15% apatite and 16% ilmenite. The complex is a circular intrusion, 80 km in diameter, reflecting three major Cambrian magmatic cycles. The first cycle is divided into the Lower Series of unlayered troctolites and the 3 km thick Layered Series of troctolites, olivine gabbros and gabbros, containing more than 15% Fe-Ti oxides and terminating in the 250 m thick Critical Zone that hosts the deposits. The rocks of the 10 m Nelsonite Subzone contain more than 90% Fe-Ti oxides and apatite, the latter exceeding 25 wt%. The 150 m Gabbro-Nelsonite Subzone has more than 50% nelsonite in its lower half, while the proportion of silicates increases upwards. Fractionation of the nelsonites could have been favoured by enrichment of the parent magmas in Fe, Ti and P before their final emplacement. Production is projected at 4 000 000 t/a by open pit, yielding 600 000 t/a apatite and 330 000 t/a ilmenite concentrates.