[HRE16-P02] Ni-Cu-PGM Mineralisation in the Bastard Reef and Merensky Reef of the Flatreef section, Turfspruit Farm, Northern Limb, Bushveld Igneous Complex, South Africa.
Keywords:Ni-Cu-PGM, Bushveld Igneous Complex, Flatreef Section, Northern Limb
Logging and petrographical investigations revealed the Bastard Reef to comprise a fine to medium-grained equigranular feldspathic orthopyroxenite. Several metres below the Bastard Reef lies the Merensky Reef, which has been subdivided into 3 different units (M2, M1U and M1L) mainly based on mineralogical and textural variations. The M2 is the uppermost layer comprising medium to coarse-grained equigranular orthopyroxenite, denoted by cumulus orthopyroxene and is bound irregularly by a chromite seam at its top contact. The M2 orthopyroxenite is underlain by the M1U denoted by a cumulate textured pegmatoidal orthopyroxenite and is commonly bound by a chromite stringer at its top contact and a less consistent one at its base. The M1L, which is laterally less continuous, comprises a poikilitic textured harzburgite and/or varied-textured olivine-bearing orthopyroxenite. SEM analysis revealed sulphide mineral assemblages in the reefs usually comprising pyrrhotite, pentlandite and chalcopyrite as fine to medium-grained disseminations, blebs and net-textured sulphides. PGM mineralisation comprise a wide range of PGMs, mostly Platinum and Palladium dominated, grouped into bismithotellurides (-Bi-Te), antimonides, arsenides, Fe and Sn alloys, sulphides, as well as laurite (RuS2) and Ir-Ru-Rh-Pt-Pd sulfoarsenides alongside chromite seams. Semi-quantitative analysis illustrates the Flatreef section to be an undisturbed magmatic sequence that is much less affected by assimilation and contamination. It retains much of its magmatic characteristics and provides a great opportunity to furthermore study magmatic processes that resulted in the formation of such an enigmatic deposit.
Grobler, D.F., Brits, J.A.N., Maier, W.D. and Crossingham, A. (2018) Litho- and Chemostratigraphy of the Flatreef PGE deposit, northern Bushveld Complex. Mineralium Deposita, 126, 1-26.
Kinnaird, J.A., Hutchinson, D., Schurman, L., Nex, P. and de Lange, R. (2005) Petrology and Mineralisation of the Southern Platreef: Northern Limb of the Bushveld Complex, South Africa. Mineralium Deposita, 40, 576-597.