The platiniferous dunite pipes of the eastern Bushveld

Stumpel, E. F.; Rucklidge, J. C.

doi:10.2113/gsecongeo.77.6.1419

Cited by 90 publications

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“…It has been suggested that the pipes are feeders of mineralization into the stratiform reefs (Schiffries 1982, Stumpfl & Rucklidge 1982. Figure 13 shows that the PGE content and relative proportions do not appear to be influenced by proximity to a pipe, although the mineral assemblage was.…”

Section: Discussionmentioning

confidence: 98%

Relationship Between Pge and PGM in the Bushveld Complex

Cawthorn¹,

Lee²,

Schouwstra³

et al. 2002

The Canadian Mineralogist

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The abundances of the platinum-group elements (PGE), and their relative proportions, are summarized for all the mines exploiting the Merensky Reef on both western and eastern limbs of the Bushveld Complex, in South Africa. Grades for the mined reef interval are uniform over 100 km of strike length, at 5-7 g/t, except for Union mine, where it is currently 8 g/t. The relative proportions of the various PGE are extremely constant over this same distance. In contrast, the platinum-group minerals (PGM) vary enormously. On a regional scale around the western limb, the mineralogy ranges from alloy-dominated in the northwest to sulfide-or telluride-arsenide-dominant in the southeast. Local features that are important in terms of mining are potholes and discordant ultramafic bodies. Comparative studies of the PGE from close to and within such structures again show constant absolute and relative abundances. Limited data on the PGE from PGE-mineralized pipes (Onverwacht, Mooihoek and Driekop) suggest that they are Pt-dominated, and have a totally different relative pattern of distribution of the PGE than that in the stratiform mineralization. The PGM in the vicinity of these pipes also tends to be dominated by alloys, and in potholes by alloys and tellurides and arsenides. Hence, on both a regional scale and very local scale associated with disturbances in the reef, there is a dichotomy between the constancy of the PGE and the variability of the PGM. These observations suggest that the primary mechanism concentrating the PGE is a first-order process, and that the evolution of the PGM is the result of secondary processes related to cooling, local changes in f(S 2 ) in the crystallization environment, and subsolidus re-equilibration. The debate as to whether the PGE are derived by fluid scavenging of a footwall succession or have accumulated from supernatant magma is reexamined, and unresolved problems pertaining to both processes are highlighted.Keywords: Bushveld Complex, platinum-group elements, platinum-group mineralogy, Merensky Reef, potholes, pipes, mineralization, South Africa. SOMMAIRELe niveau de concentration des éléments du groupe du platine (EGP), ainsi que leurs proportions relatives, sont examinés pour toutes les mines exploitant le banc de Merensky, dans les secteurs ouest et est du complexe de Bushveld, en Afrique du Sud. Les teneurs des sections exploitées de ce banc sont uniformes, entre 5 et 7 g/t, sur une distance de 100 km, sauf à la mine Union, où la teneur est présentement 8 g/t. Les proportions relatives des EGP sont d'une constance frappante sur cette distance. En revanche, les assemblages de minéraux du groupe du platine varient énormément. Sur une échelle régionale autour du secteur ouest, ces minéraux vont d'alliages dans le nord-ouest aux minéraux sulfurés ou bien aux tellurures et arséniures vers le sud-est. Les "nidsde-poule" et les venues ultramafiques discordantes sont des accidents locaux qui exercent une influence sur les activités minières. Des études comparatives des EGP près de ...

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Section: Discussionmentioning

confidence: 98%

Relationship Between Pge and PGM in the Bushveld Complex

Cawthorn¹,

Lee²,

Schouwstra³

et al. 2002

The Canadian Mineralogist

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“…It is possible that during their remobilization, Pt was selectively leached from the sulfides and deposited elsewhere in the Jinchuan system. Hydrothermal fluids can mobilize Pt without the other PGE as in the case of the hortonolite pipes of the Bushveld Complex (Stumpfl and Rucklidge, 1982;Rowell and Edgar, 1985) or Pd and Pt as in the case of the ''hydrothermal" Cu-Ni sulfide stringers in the footwall basalts at Kambalda Keays, 1984, 2002;Lesher and Stone, 1996).…”

Section: Negative Pt-anomaly In the Massive Oresmentioning

confidence: 99%

Siderophile and chalcophile elemental constraints on the origin of the Jinchuan Ni-Cu-(PGE) sulfide deposit, NW China

Song

Keays

Zhou

et al. 2009

Geochimica et Cosmochimica Acta

103

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“…In the Bushveld Complex, evidence for general hydrothermal activity is found in hydrothermal veins and fluid inclusions therein (Boudreau et al 1986;Schiffries and Skinner 1987), and the effects of fluids on chromit(it)e were repeatedly discussed (Stumpfl and Rucklidge 1982;Merkle 1988Merkle , 1992McCandless et al 1999;Penberthy and Merkle 1999).…”

Section: Reasons For Intermediate (Metastable?) Compositionsmentioning

confidence: 99%

Cooperite and braggite from the Bushveld Complex: implications for the miscibility gap and identification

Merkle

Verryn

2003

Miner Deposita

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Analyses of the Pt-Pd±Ni sulphides cooperite, braggite, and vysotskite reported from worldwide occurrences seem to imply a continuum of compositions between vysotskite and cooperite, with no obvious miscibility gap. This is contrary to the experimentally confirmed miscibility gap between cooperite and braggite, and the established compositional gap between co-existing cooperite and braggite from the Merensky Reef. Although the only unambiguous way of distinguishing between cooperite and braggite is to obtain structural information through X-ray diffraction or equivalent techniques, most identification of Pt-Pd±Ni sulphides is based on microanalytical techniques due to the small grain size of most platinum-group minerals. Ni contents also have to be considered because a classification based on the Pt/Pd ratio alone can be very misleading. Naming of Pt-Pd±Ni sulphide compositions with high Pt contents based on qualitative or semiquantitative analyses should be avoided. Natural PtPd±Ni sulphides which project into the compositional gap (established by experimental work) cannot be named without supporting structural information. Compositions of grains, which plot inside the gap, are considered to be metastable and to result from the loss of Pd through interaction with hydrothermal fluids.Keywords Braggite AE Cooperite AE Pt-Pd-Ni-S AE Miscibility gap AE Bushveld AE South Africa Recent experimental investigations of the system PtS- PdS-NiS (Verryn and Merkle 2000, 2002) confirmed the presence of a miscibility gap between cooperite and braggite and a continuous solid solution series between braggite and vysotskite. Contrary to the experimentally confirmed miscibility gap between cooperite and braggite, a compilation of analyses reported in the literature from worldwide occurrences seems to imply a continuum of compositions between vysotskite and cooperite with no obvious gap (Fig. 1). This contribution focuses on the reasons for the discrepancy between experiments and natural occurrences. The question also arises of which criteria to use for identification of minerals inside the experimentally established miscibility gap. The data baseA compilation of published analyses from the literature (for sources see caption of Fig. 1) was used to evaluate the miscibility gap between cooperite and braggite and the problem of identifying some natural Pt-Pd-Ni sulphides. The database of 592 microprobe analyses from Miner Deposita (2003) 38: 381-388

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The platiniferous dunite pipes of the eastern Bushveld

Cited by 90 publications

References 0 publications

Relationship Between Pge and PGM in the Bushveld Complex

Relationship Between Pge and PGM in the Bushveld Complex

Siderophile and chalcophile elemental constraints on the origin of the Jinchuan Ni-Cu-(PGE) sulfide deposit, NW China

Cooperite and braggite from the Bushveld Complex: implications for the miscibility gap and identification

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