Major and trace element geochemistry of the Platreef on the farm Townlands, northern Bushveld Complex

Manyeruke, Tawanda D.

doi:10.2113/108.3.381

Cited by 49 publications

(38 citation statements)

References 23 publications

(30 reference statements)

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“…Close examination of the contact and three dimensional mapping of the contact in the Zwartfontein open pit (Holwell and Jordaan 2006) shows conclusively that in terms of geometry the Platreef is a sill-like body or network of sills (see also Kinnaird 2005;Manyeruke et al 2005) that was intruded, solidified, and sheared before intrusion of the gabbronorites and that similar country rocks formed the floor and roof of the Platreef. The gabbronorites overlying the Platreef do not represent a magma column that could have supplied Ni, Cu and PGE.…”

Section: Introductionmentioning

confidence: 94%

Did lower zone magma conduits store PGE-rich sulphides that were later supplied to the Platreef?

McDonald¹,

Holwell²

2007

South African Journal of Geology

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The Platreef in the northern limb of the Bushveld Complex comprises pyroxenites and gabbros that contain enormous quantities of Ni, Cu and platinum-group elements (PGE) concentrated from a larger volume of magma than represented by the Platreef itself. Chill zones and cross-cutting relationships between the Platreef pyroxenites and hanging wall norites show that the Platreef was originally a relatively thin, sill-like, intrusion or sill network without an overlying magma column. Lower Zone cumulates pre-date the Platreef and show depletion in Ni and Cu compared with similar rocks elsewhere in the Bushveld, suggesting that they interacted with sulphides in a sub-chamber or conduit. In order to overcome the mass balance paradox imposed by the absence of an overlying magma a new model for the development of the Platreef is proposed whereby Ni, Cu and PGE were concentrated in conduits that fed magma chambers of the Lower Zone and that these sulphides were transported by a later magma into the Platreef.

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Section: Introductionmentioning

confidence: 94%

Did lower zone magma conduits store PGE-rich sulphides that were later supplied to the Platreef?

McDonald¹,

Holwell²

2007

South African Journal of Geology

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“…The Platreef of the Bushveld Complex (due to its large size and attractive metal tenors) is currently the only contact-type PGE mineralization mined. The Platreef is defined as "a lithologically variable unit dominated by pyroxenite, which is irregularly mineralized with PGE, Cu and Ni, between the Transvaal metasedimentary footwall or the Archean basement and the overlying Main Zone gabbronorite" Manyeruke et al 2005;McDonald and Holwell 2011;Yudovskaya et al 2012). The mineralization is hosted within vari-textured pyroxenites, norites and gabbros with rare peridotites and chromitites.…”

Section: "Contact-type" Pge-mineralizationmentioning

confidence: 99%

“…c Base-metal and platinum-group element concentrations of pyroxenite from various localities within the Platreef. The data are extracted from McDonald (2006, 2007) and Manyeruke et al (2005). d Base-metal and platinum-group element concentrations across the concentrated towards the base and the upper contact of the layer .…”

Section: Pge-mineralization Associated With Large Chromitite Layersmentioning

confidence: 99%

Platinum-Group Element Deposits in Layered Intrusions: Recent Advances in the Understanding of the Ore Forming Processes

Godel

2015

Springer Geology

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“…Within the northern limb, Platreef mineralization is present within a 10-400 m thick basal unit, intruded as a series of sills (Kinnaird 2005) that rests directly on Palaeoproterozoic sediments and Archaean gneisses and granites and is overlain by Main Zone gabbronorites. Widespread contamination of the Platreef magma through assimilation of differing floor rocks along its strike length largely accounts for the complexity of the deposit, which formed through the interaction of magmatic, metasomatic, and hydrothermal processes (e.g., Harris and Chaumba 2001;Armitage et al 2002;Manyeruke 2003;Hutchinson and Kinnaird 2005;Kinnaird 2005;Manyeruke et al 2005;Sharman-Harris et al 2005;McDonald 2006, 2007;Holwell et al , 2011Hutchinson and McDonald 2008;McDonald et al 2009;Sharman et al 2013). Gruenewaldt et al (1989).…”

Section: Introductionmentioning

confidence: 99%

“…Inset map of the entire Bushveld Complex adapted from Eales and Cawthorn (1996) The Platreef (sensu stricto) is present only north of the Ysterberg-Planknek Fault (Kinnaird and McDonald 2005;Fig. 1), and represents a package of texturally heterogeneous and variably altered pyroxenitic lithologies, which is irregularly mineralized with sulfide associated PGE, Ni, and Cu (e.g., Armitage et al 2002;Kinnaird 2005;Hutchinson and Kinnaird 2005;Hutchinson and McDonald 2008;Manyeruke et al 2005;McDonald and Holwell 2011). To the south of Ysterberg-Planknek Fault, a distinct layered package of PGE-bearing mafic cumulates termed the Grasvally Norite-Pyroxenite-Anorthosite (GNPA) member is developed (Hulbert 1983).…”

Section: Introductionmentioning

confidence: 99%

Precious and base metal geochemistry and mineralogy of the Grasvally Norite–Pyroxenite–Anorthosite (GNPA) member, northern Bushveld Complex, South Africa: implications for a multistage emplacement

2014

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The Grasvally Norite-Pyroxenite-Anorthosite (GNPA) member within the northern limb of the Bushveld Complex is a mineralized, layered package of mafic cumulates developed to the south of the town of Mokopane, at a similar stratigraphic position to the Platreef. The concentration of platinum-group elements (PGE) in base metal sulfides (BMS) has been determined by laser ablation inductively coupled plasma-mass spectrometry. These data, coupled with wholerock PGE concentrations and a detailed account of the platinum-group mineralogy (PGM), provide an insight into the distribution of PGE and chalcophile elements within the GNPA member, during both primary magmatic and secondary hydrothermal alteration processes. Within the most unaltered sulfides (containing pyrrhotite, pentlandite, and chalcopyrite only), the majority of IPGE, Rh, and some Pd occur in solid solution within pyrrhotite and pentlandite, with an associated Pt-As and Pd-Bi-Te dominated PGM assemblage. These observations in conjunction with the presence of good correlations between all bulk PGE and base metals throughout the GNPA member indicate the presence and subsequent fractionation of a single PGE-rich sulfide liquid, which has not been significantly altered. In places, the primary sulfides have been replaced to varying degrees by a low-temperature assemblage of pyrite, millerite, and chalcopyrite. These sulfides are associated with a PGM assemblage characterized by the presence of Pd antimonides and Pd arsenides, which are indicative of hydrothermal assemblages. The presence of appreciable quantities of IPGE, Pd and Rh within pyrite, and, to a lesser, extent millerite suggests these phases directly inherited PGE contents from the pyrrhotite and pentlandite that they replaced. The replacement of both the sulfides and PGM occurred in situ, thus preserving the originally strong spatial association between PGM and BMS, but altering the mineralogy. Precious metal geochemistry indicates that fluid redistribution of PGE is minimal with only Pd, Au, and Cu being partially remobilized and decoupled from BMS. This is also indicated by the lower concentrations of Pd evident in both pyrite and millerite compared with the pentlandite being replaced. The observations that the GNPA member was mineralized prior to intrusion of the Main Zone and that there was no local footwall control over the development of sulfide mineralization are inconsistent with genetic models involving the in situ development of a sulfide liquid through either depletion of an overlying magma column or in situ contamination of crustal S. We therefore believe that our observations are more compatible with a multistage emplacement model, where preformed PGE-rich sulfides were emplaced into the GNPA member. Such a model explains the development and distribution of a single sulfide liquid throughout the entire 400-800 m thick succession. It is therefore envisaged that the GNPA member formed in a similar manner to its nearest analogue the Platreef. Notable differences however in PGE teno...

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Major and trace element geochemistry of the Platreef on the farm Townlands, northern Bushveld Complex

Cited by 49 publications

References 23 publications

Did lower zone magma conduits store PGE-rich sulphides that were later supplied to the Platreef?

Did lower zone magma conduits store PGE-rich sulphides that were later supplied to the Platreef?

Platinum-Group Element Deposits in Layered Intrusions: Recent Advances in the Understanding of the Ore Forming Processes

Precious and base metal geochemistry and mineralogy of the Grasvally Norite–Pyroxenite–Anorthosite (GNPA) member, northern Bushveld Complex, South Africa: implications for a multistage emplacement

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