Kambalda type komatiitic nickel ore deposits
Kambalda type komatiitic nickel ore deposits are a class of magmatic iron-nickel-copper-platinum-group element ore deposit in which the physical processes of komatiite volcanology serve to deposit, concentrate and enrich a Fe-Ni-Cu-(PGE) sulfide melt within the lava flow environment of an erupting komatiite volcano. The classification of the type of ore environment sets these apart from other magmatic Ni-Cu-PGE ore deposits, which share many of the same genetic (formational) controls. Kambalda-type ore deposits are distinctive in that the deposition of an immiscible Fe-Ni-Cu sulfide melt occurs within a lava flow channel upon the palaeosurface. This is distinct from other magmatic Ni-Cu-PGE deposits, where Fe-Ni-Cu sulfide melt accumulates within a subvolcanic feeder dike, sill, or magma chamber. The genetic model of Kambalda-type Ni-Cu-(PGE) ore deposits is similar that of many other magmatic Ni-Cu-PGE ore deposits: Metal Source: komatiitic magma, which has been generated by high-degree partial melting of the mantle and which was strongly undersaturated in sulfide in the source (Wendlandt, 1982; see also Mavrogenes and O'Neill, 1999) Sulfur Source: S-rich country rocks (sulfidic sediments and volcanic rocks), from which the sulfide is melted by the high-temperature komatiite magma Dynamic System: Ni-Cu-Co-PGE are chalcophile and will preferentially partition from the silicate melt into the sulfide melt. The metal tenors (abundances in 100% sulfide) are enhanced by the flushing of voluminous komatiitic melt across the sulfide accumulation. Physical Trap: depressions in the footwall rocks, which may represent volcanic topographic irregularities modified by thermomechanical erosion. Sulfides within the komatiite lava flows are denser than the silicate melt and tend to pool within topographic lows, which may be enhanced in the lava channel by proposed thermal erosion of the substrate by the komatiite lava. Recent research on the S isotopic compositions of komatiitic sulfides (Bekker et al.