Petrogenesis of thick, high-grade PGE mineralisation in the Flatreef, northern Bushveld Complex

Maier, Wolfgang D.; Barnes, Stephen J.; Godel, Bélinda; Grobler, Danie; Smith, William

doi:10.1007/s00126-022-01156-6

Cited by 2 publications

(1 citation statement)

References 57 publications

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“…The Flatreef mineralised zone is interpreted as the down-dip extension of the Platreef (Kekana 2014;Grobler et al 2019;Maier et al 2021Maier et al , 2023. A recent stratigraphic interpretation for the Flatreef on the farms Turfspruit and Macalacaskop by Grobler et al (2019) strengthens its correlation to the Critical Zone as found elsewhere in the Bushveld Complex, but suggests that the Flatreef is controlled by a distinctive structural style, the origin of which is not yet determined.…”

Section: Introductionmentioning

confidence: 98%

Structural context of the Flatreef in the Northern Limb of the Bushveld Complex

Brits,

Grobler,

Crossingham

et al. 2024

Miner Deposita

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The Flatreef occurs at a depth of 700 m under the farm Turfspruit 241 KR in the Northern Limb of the Bushveld Complex. The Flatreef forms part of the Platreef of the Northern Limb, which contains magmatic rocks of the Rustenburg Layered Suite of the Bushveld Complex. The structure of the Flatreef is a flat-lying to gently westerly dipping monoclinal to open fold, 1 km wide and 6 km long. Distinctive features within the Flatreef include the development of cyclical magmatic layering with locally thickened pyroxenitic layers, and associated economically significant poly-metallic mineralisation. Geophysical evidence, exploration drill core, and recent underground exposure show that deformation had a major influence on the Flatreef mineralization. Block faulting and first generation folding affected the orientation and shape of the sedimentary host-rock sequence prior to intrusion of the Rustenburg Layered Suite. These structural and host-rock elements controlled the intrusion of the Lower Zone, and to a lesser degree, the Critical Zone correlatives of the Bushveld Complex in the Northern Limb. During intrusion reverse faults and shear zones and a second generation of folds were active, as well as local extension along layering. Syn-magmatic deformation on these structures led to laterally extensive stratal thickening across them, including the Merensky-Reef correlative that forms part of the Flatreef. This deformation was likely to have been driven by subsidence of the Bushveld complex. Many of these structures were intruded by granitic magmas during the late stages of intrusion, and they were reactivated during extension after intrusion. Thus, structures were active before, during and after the intrusion of Northern Limb, and the structural evolution determined the current geometry and mineral endowment of the Flatreef.

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Section: Introductionmentioning

confidence: 98%

Structural context of the Flatreef in the Northern Limb of the Bushveld Complex

Brits,

Grobler,

Crossingham

et al. 2024

Miner Deposita

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Petrogenesis of Ni-sulfide mineralisation in the ca. 3.0 Ga Maniitsoq intrusive belt, western Greenland

Maier,

Muir,

Barnes

et al. 2024

Miner Deposita

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The ca. 3.0 Ga Ni sulfide mineralisation at Maniitsoq, SW Greenland, is hosted by a cluster of relatively small, irregularly shaped mafic-ultramafic intrusions, typically 10s of m to a few km across, that are lodged within broadly coeval gneiss. Many of the intrusions are fault bounded and fragmented so that their original sizes remain unknown. The sulfides form disseminations and sulfide matrix breccia veins displaying sharp contacts to the host intrusives. The mineralisation has relatively high Ni/Cu, with 4–10% Ni and 1–2% Cu. Correlations between Ni and Cu with sulfide content are strong, consistent with a magmatic origin of the mineralisation. PGE contents are mostly below 0.5 ppm, and Cu/Pd is typically above primitive mantle levels, interpreted to reflect equilibration of the parent magma with segregating sulfide melt prior to final magma emplacement. Sulfide segregation was likely triggered by assimilation of crustal sulfur, as suggested by whole rock S/Se ratios of 7000–9000. The sulfide melt underwent extensive fractionation after final emplacement, caused by downward percolation of Cu-rich sulfide melt through incompletely solidified cumulates. We suggest that the exposed Maniitsoq intrusions represent the Ni-rich upper portions of magma conduits implying that there is potential for Cu-rich sulfides in unexposed deeper portions of the belt.

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Petrogenesis of thick, high-grade PGE mineralisation in the Flatreef, northern Bushveld Complex

Cited by 2 publications

References 57 publications

Structural context of the Flatreef in the Northern Limb of the Bushveld Complex

Structural context of the Flatreef in the Northern Limb of the Bushveld Complex

Petrogenesis of Ni-sulfide mineralisation in the ca. 3.0 Ga Maniitsoq intrusive belt, western Greenland

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