Characterizing the mineralogy of orthomagmatic Fe–Ti–V (± P) oxide mineralization hosted in Paleoproterozoic anorthosite in the Cape Caribou River Allochthon, Grenville Province, Southeast Labrador

English Abstract:

The Cape Caribou River Allochthon (CCRA) is a thick lobate thrust slab located in the Grenville Province of south-eastern Labrador. It consists mainly of Paleoproterozoic anorthosite-mangerite-charnockite-granitoid rocks. The uppermost unit of the CCRA is the North-West River Anorthosite (~1625 Ma), a heterogeneous unit containing rocks ranging from anorthosite to gabbronorite, which are host to Fe–Ti–V (± P) oxide mineralization. Exploration activity in the CCRA has been sparse, despite several known mineralized areas. Ongoing research is investigating the mineralogy, geochemistry, and mineral chemistry of oxide mineralization to understand the origin of mineralization, and to provide insights into exploration potential of the CCRA and similar geological settings; amenability of oxides to beneficiation is also explored. Preliminary results are presented herein.

Fe–Ti–V (± P) oxide mineralization in the CCRA is abundant and widespread, and has four modes of occurrence: (1) pods of semi-massive to massive oxide (apatite-poor and -rich); (2) oxide veins (with straight or irregular contacts with host rocks); (3) disseminated oxide (mineralization occurring on its own or associated with orthopyroxene); and (4) alternating oxide bands having sharp contact with host rocks. All mineralization occurrences consist of spinel series (ulvospinel-magnetite solid solution) and trigonal series (ilmenite-hematite solid solution) Fe-Ti oxides, and are associated with pyrrhotite, chalcopyrite and pyrite. The mineralization exhibits complex mineral associations between oxides, apatite, silicates and sulfides, and within each mineral group; complex and variable exsolution textures within oxide minerals (magnetite, ilmenite, hematite and hercynite) are abundant. These mineral relationships will be used to determine the oxide mineral paragenesis, the partitioning and residence of Ti and V, the physiochemical conditions of oxide formation, and the processing route for oxide concentrate.