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

Prevec, Stephen A.

doi:10.12789/geocanj.2018.45.138

Cited by 6 publications

(1 citation statement)

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“…Because many mafic-ultramafic intrusions hosting classical Fe–Ti–V deposits also contain significant chromite, PGE, Ni, Cu, Co, apatite and other resources (e.g. Von Gruenewaldt 1993; Naldrett et al 2012; Maier et al 2013; Prevec 2018; Smith and Maier 2021), such intrusions represent geological environment with an exceptional multi-commodity exploration potential.…”

Section: Main Vanadium-bearing Ore Depositsmentioning

confidence: 99%

Vanadium as a critical material: economic geology with emphasis on market and the main deposit types

Simandl

Paradis

2022

Applied Earth Science

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Vanadium is currently considered a critical material in the European Union, the U.S.A., and other jurisdictions. The vanadium mine production for 2021 is estimated at more than 120 000 tonnes; however, the market base is expected to grow rapidly due to the increase in the use of vanadium for redox flow batteries. Currently, world-wide, many projects are in the advanced stages of exploration and development. In the longer term, should vanadium cease to be a critical material and the law of supply and demand applies, the marginal mines will be decommissioned, and the best deposits will remain economic. Depending on the prevailing regulations in specific jurisdictions, geological settings, and the most up-todate metallurgical research results, the main vanadium deposit types that could be considered as potential exploration and development targets are the vanadiferous titanomagnetite deposits, sandstone-hosted uranium-vanadium deposits (Salt Wash category), shale-hosted vanadium deposits, and base metal-related vanadate deposits. However, placer deposits, surficial uranium-vanadium type mineralisation, and the Minas Ragra type patrónite deposits should also be considered.

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Section: Main Vanadium-bearing Ore Depositsmentioning

confidence: 99%

Vanadium as a critical material: economic geology with emphasis on market and the main deposit types

Simandl

Paradis

2022

Applied Earth Science

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Melt infiltration in a crystal mush and pegmatoid formation in the platiniferous Merensky Reef, Bushveld Complex, South Africa

Hayes,

Maghdour-Mashhour,

Ashwal

et al. 2024

Miner Deposita

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Giant mafic-ultramafic layered intrusions of Archaean-Proterozoic age are the fossilised remnants of huge injections of silicate magma in the Earth’s crust and are our most important repositories of platinum-group elements. Magmatic PGE-rich ore deposits, such as the Merensky Reef, are typically hosted in stratiform reefs at the contacts between ultramafic and feldspathic cumulates. The Merensky Reef is commonly characterised by coarse-grained and pegmatoidal textures that may provide important clues to its origin. We present textural and in situ geochemical data for Merensky pegmatoids at Styldrift Mine (Impala Bafokeng) in the Western Bushveld Complex of South Africa. This region is adjacent to an inferred magmatic feeder zone to the Bushveld. The Merensky pegmatoids are characterised by (i) amoeboid olivine inclusions in zoned orthopyroxene megacrysts with increasing molar Mg# of orthopyroxene towards olivine, (ii) fine-grained chains of orthopyroxene in compositional equilibrium with adjacent orthopyroxene megacrysts, (iii) increasing molar Mg# of orthopyroxene megacrysts and increasing molar An with decreasing 87Sr/86Sri (at 2.06 Ga) of plagioclase oikocrysts in pegmatoids laterally across a 10-km section distal to the feeder, and (iv) highly variable molar An and initial 87Sr/86Sri of interstitial plagioclase proximal to the feeder. We interpret the coarse-grained and pegmatoidal textures, their dissolution-reprecipitation features, and lateral chemical variations as the product of lateral melt infiltration and mixing in a crystal mush. We suggest that the platiniferous Merensky Reef was not formed at the base of a large melt-filled magma chamber but was instead the product of non-sequential magma emplacement that rejuvenated the crystal mush.

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Dating the Bushveld Complex: Timing of Crystallization, Duration of Magmatism, and Cooling of the World’s Largest Layered Intrusion and Related Rocks

Scoates

Wall

Friedman

et al. 2021

Journal of Petrology

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The Paleoproterozoic Bushveld Complex, including the world’s largest layered intrusion and host to world-class stratiform chromium, platinum group element, and vanadium deposits, is a remarkable natural laboratory for investigating the timescales of magmatic processes in the Earth’s crust. A framework for the emplacement, crystallization, and cooling of the Bushveld Complex based on integrated U-Pb zircon-baddeleyite-titanite-rutile geochronology is presented for samples of different rock types from the Bushveld Complex, including ultramafic and mafic cumulates, mineralized horizons, granitic rocks from the roof, and a carbonatite from the nearby alkaline Phalaborwa Complex. The results indicate that (1) the Bushveld Complex was built incrementally over a ∼5 million-year interval from 2060 Ma to 2055 Ma with a peak in magma flux at c.2055–2056 Ma, (2) U-Pb zircon crystallization ages do not decrease in an uninterrupted systematic manner from the base to the top of the intrusion indicating that the Bushveld Complex does not represent the crystallized products of a single progressively filled and cooled magma chamber, and (3) U-Pb rutile dates constrain cooling of the intrusion at the level of the Critical Zone through ∼500 °C by 2053 Ma. The c.2060 Ma Phalaborwa Complex (pyroxenite, syenite, carbonatite + Cu-Fe-phosphate-vermiculite deposits) represents one of the earliest manifestations of widespread Bushveld-related magmatism in the northern Kaapvaal craton. The extended range and out-of-sequence U-Pb zircon dates determined for a harzburgite from the Lower Zone (c.2056 Ma), an orthopyroxenite from the Lower Critical Zone (c.2057 Ma), and orthopyroxenites from the Upper Critical Zone (c.2057–2060 Ma) are interpreted to indicate that the lower part of the Bushveld Complex developed through successive intrusions and accretion of sheet-like intrusions (sills), some intruded at different stratigraphic levels. Crystallization of the main volume of the Bushveld Complex, as represented by the thick gabbroic sequences of the Main Zone and Upper Zone, is constrained to a relatively narrow interval of time (∼1 million years) at c.2055–2056 Ma. Granites and granophyres in the roof, and a diorite in the uppermost Upper Zone, constitute the youngest igneous activity in the Bushveld Complex at c.2055 Ma. Collectively, these results contribute to an emerging paradigm shift for the assembly of some ultramafic-mafic magmatic systems from the conventional “big tank” model to an “amalgamated sill” model. The volume-duration relationship determined for magmatism in the Bushveld Complex, when compared to timescales established for the assembly of other layered intrusions and more silica-rich plutonic-volcanic systems worldwide, is distinct and equivalent to those determined for Phanerozoic continental and oceanic flood basalts that constitute large igneous provinces. Emplacement of the 2055–2060 Ma Bushveld Complex corresponds to the end of the Lomagundi-Jatuli Event, the largest magnitude positive carbon isotope excursion in Earth history, and this temporal correlation suggests that there may have been a contribution from voluminous Bushveld ultramafic-mafic-silicic magmatism to disruptions in the global paleoenvironment.

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

Cited by 6 publications

References 91 publications

Vanadium as a critical material: economic geology with emphasis on market and the main deposit types

Vanadium as a critical material: economic geology with emphasis on market and the main deposit types

Melt infiltration in a crystal mush and pegmatoid formation in the platiniferous Merensky Reef, Bushveld Complex, South Africa

Dating the Bushveld Complex: Timing of Crystallization, Duration of Magmatism, and Cooling of the World’s Largest Layered Intrusion and Related Rocks

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