Re-Os and S isotope evidence for the origin of Platreef mineralization (Bushveld Complex)

Yudovskaya, Marina A.; Белоусова, Е. А.; Kinnaird, Judith A.; Дубинина, Е. О.; Grobler, D. F.; Pearson, Norman J.

doi:10.1016/j.gca.2017.07.029

Cited by 21 publications

(13 citation statements)

References 101 publications

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“…Stable isotope (S, O) compositions are consistent with significant footwall-derived contributions to the Bushveld magma, but also may indicate both local and pre-emplacement contamination and sulphur saturation, as well as secondary fluid involvement (Sharman- Harris et al 2005). More recent examination of Re-Os and S isotopes in sulphides specifically indicates that while the Lower Zone ultramafic rocks show evidence for local S, the overlying Platreef is dominated by magmatic mantle sulphur (Yudovskaya et al 2017a). Due to the heterogeneous nature of the local footwall (which includes granite, banded iron formation, carbonate rocks and shale), the nature of the magmatic-hosted footwall-rich basal breccia displays significant lateral variation, further complicated by structural control on the footwall (Nex 2006).…”

Section: Nature Of the Platreefmentioning

confidence: 72%

Igneous Rock Associations 23. The Bushveld Complex, South Africa: New Insights and Paradigms

Prevec

2019

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Section: Nature Of the Platreefmentioning

confidence: 72%

Igneous Rock Associations 23. The Bushveld Complex, South Africa: New Insights and Paradigms

Prevec

2019

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“…In contrast, pentlandite PGE concentrations from Turfspruit are commonly below the detection limit, except for Pd, which often has concentrations of~10 ppm [22]. The pentlandite PGE concentrations from Aurora display values below tens of ppm for Pt, Rh, Ru, Os and Ir, and 30 ppm for Pd [29], whereas Pd concentrations in pentlandite for the Flatreef can range up to 500 ppm [19]. The pentlandite Pd concentrations display a broad range concerning the location (i.e., Overysel, Sandsloot and Aurora) and the host rock type (cf.…”

Section: Pge In Bmsmentioning

confidence: 96%

“…Even though there is broad agreement on the magmatic origin of the Platreef, its sulphide mineralization mechanism is still at the centre of the scientific debate [1,2,19,44]. In particular, the composition of the Platreef footwall's clinopyroxenite (and thus the associated sulphide mineralization) fails to reconcile with a purely magmatic evolution, and suggests modification by country rock assimilation and/or interaction with hydrothermal fluids.…”

Section: Sulphide Mineralization and Distribution Of Pgesmentioning

confidence: 99%

“…The isotope ratios of the three analyzed sulphide phases in OY541 (chalcopyrite, pentlandite, pyrrhotite) are indicative of the mass-independent fraction of sulphur (MIFS), expressed as ∆ 33 S ( Figure 12B). MIFS is almost exclusively found in rocks older than the great oxidation event, i.e., older than 2.45 Ga [19,[92][93][94]. This implies that the sulphide phases crystallized from pristine Bushveld magmas (i.e., 2.054 Ga) are not expected to show MIFS, unless sulphur was assimilated from a significantly older source.…”

Section: Sulphide Mineralization and Distribution Of Pgesmentioning

confidence: 99%

“…Most of these lithologies underwent, or were the product of, thermal metamorphism and hydrothermal alteration, as well as sediment assimilation, which was thought to have led to a significant change in the bulk-rock chemistry and thus mineralogy of the footwall rock types. However, the exact cause of the post-magmatic processes, and the impact on the primary igneous mineralization, is still a matter of discussion [3,5,15,18,19,49]. In order to understand the nature of these processes and their influence on the sulphide-associated PGE mineralization of the clinopyroxenites, the present study is focused on characterizing the mineralization within drill core clinopyroxenite samples from Overysel.…”

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Magmatic PGE Sulphide Mineralization in Clinopyroxenite from the Platreef, Bushveld Complex, South Africa

et al. 2020

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The Platreef, at the base of the northern limb of the Bushveld Complex in South Africa, hosts platinum-group element (PGE) mineralization in association with base-metal sulphides (BMS) and platinum-group minerals (PGM). However, whilst a magmatic origin of the stratiform mineralization of the upper Platreef has been widely confirmed, the processes responsible for the PGE and BMS mineralization and metasomatism of the host rocks in the Platreef are still under discussion. In order to contribute to the present discussion, we present an integrated petrographical, mineral-chemical, whole-rock trace- and major-element, sulphur- and neodymium-isotope, study of Platreef footwall clinopyroxenite drill core samples from Overysel, which is located in the northern sector of the northern Bushveld limb. A metasomatic transformation of magmatic pyroxenite units to non-magmatic clinopyroxenite is in accordance with the petrography and whole-rock chemical analysis. The whole-rock data display lower SiO2, FeO, Na2O and Cr (<1700 ppm), and higher CaO, concentrations in the here-studied footwall Platreef clinopyroxenite samples than primary magmatic Platreef pyroxenite and norite. The presence of capped globular sulphides in some samples, which display differentiation into pyrrhotite and pentlandite in the lower, and chalcopyrite in the upper part, is attributed to the fractional crystallization of a sulphide liquid, and a downward transport of the blebs. In situ sulphur (V-CDT) isotope BMS data show isotopic signatures (δ34S = 0.9 to 3.1 ‰; Δ33S = 0.09 to 0.32‰) close to or within the pristine magmatic range. Elevated (non-zero) Δ33S values are common for Bushveld magmas, indicating contamination by older, presumably crustal sulphur in an early stage chamber, whereas magmatic δ34S values suggest the absence of local crustal contamination during emplacement. This is in accordance with the εNd (2.06 Ga) (chondritic uniform reservoir (CHUR)) values, of −6.16 to −6.94, which are similar to those of the magmatic pyroxenite and norite of the Main Zone and the Platreef in the northern sector of the northern Bushveld limb. Base-metal sulphide textures and S–Se-ratios give evidence for a secondary S-loss during late- to post-magmatic hydrothermal alteration. The textural evidence, as well as the bulk S/Se ratios and sulphide S isotopes studies, suggest that the mineralization in both the less and the pervasively hydrothermally altered clinopyroxenite samples of Overysel are of magmatic origin. This is further supported by the PPGE (Rh, Pt, Pd) concentrations in the BMS and mass-balance calculations, in both of which large proportions of the whole-rock Pd and Rh are hosted by pentlandite, whereas Pt and the IPGE (Os, Ir, Ru) were interpreted to mainly occur in discrete PGM. However, the presence of pentlandite with variable PGE concentrations on the thin section scale may be related to variations in the S content, already at S-saturation during magmatic formation, and/or post-solidification mobilization and redistribution.

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Distribution of platinum-group elements in pristine and near-surface oxidized Platreef ore and the variation along strike, northern Bushveld Complex, South Africa

et al. 2018

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Re-Os and S isotope evidence for the origin of Platreef mineralization (Bushveld Complex)

Cited by 21 publications

References 101 publications

Igneous Rock Associations 23. The Bushveld Complex, South Africa: New Insights and Paradigms

Igneous Rock Associations 23. The Bushveld Complex, South Africa: New Insights and Paradigms

Magmatic PGE Sulphide Mineralization in Clinopyroxenite from the Platreef, Bushveld Complex, South Africa

Distribution of platinum-group elements in pristine and near-surface oxidized Platreef ore and the variation along strike, northern Bushveld Complex, South Africa

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