Variation in Platinum Group Mineral and Base Metal Sulfide Assemblages in the Lower Group Chromitites of the Western Bushveld Complex, South Africa

Bachmann, K.‐H.; Osbahr, Inga; Tolosana‐Delgado, Raimon; Chetty, Deshenthree; Gutzmer, Jens

doi:10.3749/canmin.1700094

Cited by 10 publications

(5 citation statements)

References 48 publications

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“…Following Voordouw et al (2010) and Bachmann et al (2018), the assemblages of PGE minerals, base-metal sulfides (BMS), and silicate minerals are simplified into six groups each. For the PGE minerals, these are as follows: (1) PtPdS group (cooperite-braggite-vysotskite), (2) laurite group (laurite-ehrlichmannite: (Ru,Ir,Os)S 2 ), (3) PGE-CuS group (malanite-cuprorhodsite: Cu(Pt,Rh) 2 S 4 ), (4) PGE-FeSn alloy group (ferroplatinum, rustenburgite), (5) PGE-AsS group (hollingworthite, irarsite, ruarsite, platarsite: (Pt,Rh,Ir)AsS), (6) PGE-SbBiTePb group (geversite, insizwaite, moncheite, stibiopalladinite, sudburyite).…”

Section: Sampling and Analytical Methodsmentioning

confidence: 99%

“…Mafic dikes with the same orientation as the faults also occur. Information about the mineralogy and ore grades of the LG and MG chromitite layers at Thaba, including their PGE concentrations, is given by Bachmann et al (2018) and Kaufmann et al (2019). The Thaba mining lease is adjacent and parallel to the Amandelbult section (Dishaba and Tumela platinum mines), which exploits the UG2 and the Merensky Reef.…”

Section: Geology Of the Thaba Mine And Borehole Md17mentioning

confidence: 99%

“…From an economic standpoint, the IRUP interaction with UG2 at the Thaba mine did not significantly reduce the overall PGE grade, causing only a redistribution of grade within the layer. However, significant changes in the ore mineralogy of IRUP-affected UG2 (replacement of PGE sulfides by alloys and PGE-bearing As-Sb-Bi-Te-Pb phases) and in the assemblage (secondary talc, serpentinite) will decrease the efficiency of PGE recovery when using conventional flotation techniques (Kinloch 1982;Peyerl 1982;Penberthy et al 2000;Bachmann et al 2018).…”

Section: The Effects Of Irup On Ug2 Mineralizationmentioning

confidence: 99%

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The effects of iron-rich ultramafic pegmatite on the composition and mineralogy of the UG2 chromitite: a case study in the western Bushveld Complex, South Africa

et al. 2023

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Discordant iron-rich ultramafic pegmatites (IRUPs) intersect the UG2 chromitite at many places in the Bushveld Complex. The effects of IRUP interactions on the UG2 ore mineralogy and PGE grade are assessed at the Thaba mine, north-west Bushveld, based on a borehole profile through the UG2 layer and detailed analysis of mineral textures and compositional variations across the UG2-IRUP contacts using micro-XRF element mapping. The UG2-IRUP interaction operated at different scales and probably by different mechanisms. At the local scale (< 10 cm), a thin layer of Fe–Ti–Cr spinel and ilmenite formed on the IRUP side of the contact with UG2, whereas the UG2 chromitite developed grain coarsening, loss of interstitial silicates, and chemical gradients in Cr, Al, Fe, and Ti that extend a few centimeters from the contact into the seam. These local effects are attributed to the intrusion of IRUP melt into the solidified UG2 layer, followed by re-equilibration of the oxide minerals across the contact during cooling. On a larger scale, changes in the ore and gangue mineral assemblages in UG2 took place throughout the entire meter-thick main seam. Compared with regional UG2 compositions, chromite has higher TiO2 and lower Mg#, and there is an anomalously low abundance of interstitial plagioclase. The IRUP-affected UG2 shows relatively abundant secondary hydrous silicates, replacement of PGE sulfides by PGE alloys and PGE-As–Sb–Bi–Te–Pb phases, and formation of secondary Ni–Cu–Fe sulfides after pentlandite and chalcopyrite. These large-scale effects are attributed to hydrothermal fluids derived from IRUP melts. The IRUP bodies at the Thaba mine caused redistribution of PGE within the UG2 layer but did not significantly reduce the overall grade. However, significant changes in the ore mineral assemblage and an increased abundance of secondary silicates can reduce the efficiency of PGE recovery.

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Section: Sampling and Analytical Methodsmentioning

confidence: 99%

Section: Geology Of the Thaba Mine And Borehole Md17mentioning

confidence: 99%

Section: The Effects Of Irup On Ug2 Mineralizationmentioning

confidence: 99%

See 1 more Smart Citation

The effects of iron-rich ultramafic pegmatite on the composition and mineralogy of the UG2 chromitite: a case study in the western Bushveld Complex, South Africa

et al. 2023

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“…The BC is a layered igneous province with an area extent of 65,000 km 2 and thickness of 5–10 km (Figure 1a,b). It spans 450 km east–west and 350 km north–south (Campbell, 2011; Kawohl & Frimmel, 2016; Bachmann et al., 2018; Magson et al., 2018). The BC is Paleoproterozoic in age, dated ∼2.06 Ga.…”

Section: Site Location and Background Geologymentioning

confidence: 99%

Integration of in‐mine seismic and GPR surveys to gain advanced knowledge of Bushveld Complex orebodies

Onyebueke,

Manzi,

Rapetsoa

et al. 2023

Near Surface Geophysics

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Improving the exploration of deep‐seated mineral deposits and assessing the stability of the mine pillars require that geophysical techniques are deployed in a fast and cost‐effective manner with minimal environmental impact. This research presents results from in‐mine reflection seismic experiments and a Ground Penetrating Radar (GPR) survey conducted at Maseve platinum mine, South Africa. The research aims to develop and implement methods to image Platinum Group Metal (PGM) deposits and geological structures near mine tunnels and assess the stability of pillars. The seismic experiments were conducted using a sledgehammer source (10 lb), conventional cabled geophones (14 Hz), and a landstreamer with 4.5 Hz vertical component geophones. The GPR survey was conducted using a Noggin 500 GPR system with 500 MHz centre frequency. An image of the underlying orebody and geological structures down to 100 m from the mine tunnel floor (∼ 500 m below ground surface) was produced. We correlated the coherent reflections beneath the tunnel floor with a known Upper Group (UG2) PGM orebody. The final seismic section shows that the UG2 mineralisation is dissected by near‐vertical dykes, faults and fractures. These structures, faults in particular, are interpreted to have been active post‐mineralisation, implying that they may have contributed to the current complex geometry of the deposit. Four GPR profiles were collected around a stability pillar adjacent to the seismic lines. The radargram sections were processed to improve the S/N. The results show different patterns of fracturing and stress‐ induced structures. Perhaps, these fracturing were shown to be subvertical and constituted complex micro‐structures within the pillar, which could compromise the pillar stability and integrity. The study demonstrates that in‐mine seismic and GPR surveys can be cost‐effective and valuable for mineral exploration.This article is protected by copyright. All rights reserved

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“…Nevertheless, most methods are limited to 2D, which implies the loss of information. Techniques such as scanning electron microscopy (SEM), electron probe microanalysis (EPMA) or transmission electron microscopy (TEM) are commonly used in numerous application [ 4–11 ] . However, usually, the investigated features of a sample are 3‐dimensional, thus a complete characterization would only be possible using a 3D technique.…”

Section: Introductionmentioning

confidence: 99%

Spectral X‐ray computed micro tomography: 3‐dimensional chemical imaging

et al. 2020

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We present a new approach to 3‐dimensional chemical imaging based on X‐ray computed micro tomography (CT), which enables the analysis of the internal elemental chemistry. The method uses a conventional laboratory‐based CT scanner equipped with a semiconductor detector (CdTe). Based on the X‐ray absorption spectra, elements in a sample can be distinguished by their specific K‐edge energy. The capabilities and performance of this new approach are illustrated with different experiments, i.e. single pure element particle measurements, element differentiation in mixtures, and mineral differentiation in a natural rock sample. The results show that the method can distinguish elements with K‐edges in the range of 20 to 160 keV, this corresponds to an element range from Ag to U. Furthermore, the spectral information allows a distinction between materials, which show little variation in contrast in the reconstructed CT image.

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Variation in Platinum Group Mineral and Base Metal Sulfide Assemblages in the Lower Group Chromitites of the Western Bushveld Complex, South Africa

Cited by 10 publications

References 48 publications

The effects of iron-rich ultramafic pegmatite on the composition and mineralogy of the UG2 chromitite: a case study in the western Bushveld Complex, South Africa

The effects of iron-rich ultramafic pegmatite on the composition and mineralogy of the UG2 chromitite: a case study in the western Bushveld Complex, South Africa

Integration of in‐mine seismic and GPR surveys to gain advanced knowledge of Bushveld Complex orebodies

Spectral X‐ray computed micro tomography: 3‐dimensional chemical imaging

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