A review of the emplacement and formation of magmatic platinum-group elements-enriched deposits in large layered mafic/ultramafic intrusions, with special reference to the “big three” (Stillwater Complex, Great Dyke, and Bushveld Complex)

Layered intrusions occur on every continent and in rocks ranging in age from Neoarchean to the Tertiary. The “big three” large layered mafic intrusions (Stillwater Complex, Great Dyke, and Bushveld Complex), belong to this select group not only because of their economic importance since they constitute ∼94% of the world's reserves of platinum-group elements (PGEs), but also because of their immense sizes and continuity of individual layers across dozens of kilometers. The “big three” were all emplaced in the Precambrian (Neoarchean to Paleoproterozoic) Era.