Henriëtte Ueckermann

University of Johannesburg

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Fanus Viljoen

University of Johannesburg

Robert Bolhar

University of the Witwatersrand

Marlina Elburg

University of Johannesburg

Linda M. Iaccheri

University of the Witwatersrand

G. M. Bybee

University of the Witwatersrand

Ben Hayes

University of the Witwatersrand

Sebastian Tappe

UiT The Arctic University of Norway

D. F. Grobler

Stillwater (Canada)

Marina A. Yudovskaya

Institute of Geology of Ore Deposits Petrography Mineralogy and Geochemistry

Jiten Pattnaik

University of Johannesburg

Cooperative Institutions

Gemalto (Israel)

University of Johannesburg

Norwegian Geological Survey

Geological Survey of Sweden

University of the Witwatersrand

Geological Survey of Finland

Departamento de Ciência e Tecnologia

TU Bergakademie Freiberg

Bureau de Recherches Géologiques et Minières

Australian National University

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Bioavailable 87Sr/86Sr in European soils: A baseline for provenancing studies

The Science of The Total Environment (2019)

Jurian Hoogewerff Clemens Reimann Henriëtte Ueckermann Robert Frei Karin Margarita Frei

10.1016/j.scitotenv.2019.03.387

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Citations (113)

Geochemical and geochronological constraints on the Mesoproterozoic Red Granite Suite, Kunene AMCG Complex of Angola and Namibia

Precambrian Research (2022)

Lorenzo Milani Jérémie Lehmann G. M. Bybee Ben Hayes Trishya M. Owen-Smith

Quartz monzonite

Batholith

Petrogenesis

Geochronology

Felsic

Charnockite

10.1016/j.precamres.2022.106821

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Citations (13)

The diamond-poor nature of corundum-bearing eclogite and Karoo-type overprint of deep eclogite sources beneath the Kimberley region (Kaapvaal craton)

Journal of Petrology (2025)

Jiten Pattnaik Sonja Aulbach Fanus Viljoen Henriëtte Ueckermann Thando Mxinwa

Abstract Decades of studies have shown that the petrogenesis of kimberlite-borne cratonic eclogite and pyroxenite xenoliths reflects the endemics of their crustal protoliths and local lithosphere evolution. Detailed investigations of the origin and metasomatic history of individual eclogite xenolith suites are thus required to understand how cratonic eclogite reservoirs - and their diamond inventory - evolve in the regional tectonomagmatic context. Here, we investigate a little-studied eclogite and pyroxenite xenolith suite from the Balmoral kimberlite in the Kimberley area of the Kaapvaal craton, which, like eclogite suites in neighbouring kimberlites, likely originated as subducted Archaean oceanic crust. Detailed petrographic observations and mineral major- and trace-element analyses, combined with published data for eclogite xenoliths and eclogitic inclusions in diamond, show that this sample suite records at least two distinct episodes of metasomatic overprint: (1) Metasomatism by a kimberlite-like melt caused a decrease in clinopyroxene jadeite component and garnet grossular component and imparted high MgO and Cr2O3 contents, recorded dominantly by pyroxenite xenoliths. Comparison to Kaapvaal kimberlites and lamproites confirms that the geochemical trends cannot be reconciled with bulk kimberlite-eclogite mixing but require formation of diopside-rich clinopyroxene from the melt instead. This metasomatic style is recognised world-wide, and at Balmoral is notably restricted to the shallow lithosphere (110-150 km). (2) A distinct metasomatic event generated eclogites with extreme Y-HREE enrichment, at Balmoral restricted to the deep lithosphere (150-200 km). We propose that this enrichment style reflects garnet breakdown, with the liberation of these garnet-compatible elements to the metasomatic melt. This signature is identified in eclogite xenoliths both from early Cretaceous lamproite (Bellsbank) and late Cretaceous kimberlite (Balmoral, Kimberley) localities, tentatively ascribed to interaction with melts forming the Karoo large igneous province. Balmoral corundum-bearing eclogites derive from depths overlapping high-Ca eclogites showing a Karoo-type overprint, which significantly diluted the Al2O3 content in the bulk rock and increased silica activity as gauged by the decrease in Al[IV] in clinopyroxene, thereby destabilising corundum. Craton-wide, preserved corundum-bearing eclogites record diamond-stable ƒO2 and pressure conditions, yet show little compositional overlap with inclusions in eclogitic diamond. This may reflect the low propensity of COH fluids to reach carbon saturation in this lithology. The preserved corundum-bearing eclogites have reconstructed bulk major-element compositions, which, combined with small to absent Eu anomalies, suggest protoliths representing deep oceanic crustal (>0.5 GPa) cumulates of two pyroxenes plus only minor plagioclase that contained a significant melt component. The identification of such deep hybridised crustal rocks may reflect higher mantle potential temperatures and the formation of thicker oceanic crust in the Archaean.

Corundum

10.1093/petrology/egaf011

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Redox state of the Dharwar craton root as inferred from eclogite and peridotite sourced mantle cargo, with implications for kimberlite and lamproite magma formation

Contributions to Mineralogy and Petrology (2023)

Azhar M. Shaikh Yannick Bussweiler Fanus Viljoen Robert Bolhar S. Ravi

Xenolith

Peridotite

Mineral redox buffer

10.1007/s00410-023-02072-2

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Citations (2)

Identifying the origin of lead poisoning in white-backed vulture (Gyps africanus) chicks at an important South African breeding colony: a stable lead isotope approach

Environmental Science and Pollution Research (2022)

Linda van den Heever Marlina Elburg Linda M. Iaccheri Vinny Naidoo Henriëtte Ueckermann

Vulture

Lead (geology)

Isotope Analysis

10.1007/s11356-022-23209-z

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Citations (7)

The mineral chemistry derived diamond potential of NW Botswana: on- or off-craton in West Gondwanaland?

Goldschmidt Abstracts (2022)

Azhar Shaikh Sebastian Tappe Fanus Viljoen Henriëtte Ueckermann Michiel de Wit

10.46427/gold2022.10978

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Anhydrite Assimilation by Ultramafic Melts of the Bushveld Complex, and Its Consequences to Petrology and Mineralization

Marina A. Yudovskaya Sergey F. Sluzhenikin Gabi Costin К. Н. Шатагин Е. О. Дубинина

Abstract Sulfate assimilation by mafic to ultramafic melt is thought to be an important process in the genesis of magmatic PGE-Ni-Cu deposits. We consider petrological indicators and possible mechanisms of anhydrite assimilation by ultramafic melts of the northern limb of the Bushveld Complex. On farm Turfspruit, an anhydrite-bearing sedimentary raft of the Duitschland Formation separates the Platreef from underlying Lower zone peridotites. The proportion of anhydrite across the raft increases from negligible in corundum-sillimanite-magnetite hornfels at the base to 95 to 100% in anhydrite marble at the top. Underlying Lower zone peridotites lack anhydrite, whereas overlying Platreef pyroxenites contain both widespread interstitial to euhedral anhydrite as well as spherical to irregularly shaped anhydrite inclusions in association with olivine chadacrysts inside oikocrystic orthopyroxene. Olivine chadacryst compositions (Mg# 79–81 and 0.33–0.46 wt % NiO) support their pristine liquidus origin, although an association of Al-enriched orthopyroxene and interstitial anorthite indicates exchange reactions involving anhydrite and aluminosilicates from hornfels. Plagioclase from the anhydrite-contaminated rocks has an Sr isotope initial ratio (Sri) of 0.7047 to 0.7063, similar to the compositions of Bushveld early primitive magmas, in agreement with a relatively nonradiogenic signature of the anhydrite-bearing contaminant with Sri of 0.7057 to 0.7094. The range of Sri of plagioclase from the underlying Lower zone peridotites (0.7040–0.7067) and from the Turfspruit platinum reefs just below the Main zone contact (0.7068–0.7084) supports their correlation and synchronous emplacement with the Lower zone and the top of the Upper Critical zone in the western and eastern limbs of the Bushveld. The δ34S values of anhydrite (12.2–14.5‰) and a coexisting pyrrhotite-millerite-chalcopyrite sulfide assemblage (6.2–7.8‰) in a hornfelsed raft and overlying pyroxenites are interpreted to have resulted from open-system isotopic exchange, indicating closure temperatures of 750° to 820°C. The assimilation of sedimentary anhydrite is interpreted to be an important component of contact-style mineralization of the Platreef at Turfspruit that took place through the erosion and disintegration of footwall rocks by dynamic pulses of hot magmas. Chemical dissolution, thermal decomposition, and melting of sulfate-bearing rafts or xenoliths are viable assimilation processes that result in the saturation of silicate melt with sulfate, exsolution of immiscible sulfate melts, crystallization of cumulus and interstitial anhydrite, and precipitation of contact-style sulfide mineralization at the base of the intrusion. Reef-style mineralization at the top of the Platreef shows contrastingly negligible compositional and isotopic evidence of sulfate assimilation.

Ultramafic rock

Anhydrite

10.5382/sp.21.09

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Citations (7)

Hybrid norite and the fate of argillaceous to anhydritic shales assimilated by Bushveld melts

Mineralium Deposita (2020)

Marina A. Yudovskaya Gelu Costin S. F. Sluzhenikin Judith A. Kinnaird Henriëtte Ueckermann

Norite

Anorthite

Layered intrusion

Anorthosite

Pigeonite

10.1007/s00126-020-00978-6

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Citations (6)

Strontium isotope variations in the Flatreef on Macalacaskop, northern limb, Bushveld Complex: implications for the source of platinum-group elements in the Merensky Reef

Mineralium Deposita (2020)

Jarlen Jocelyn Beukes Frederick Roelofse Christoph Gauert D. F. Grobler Henriëtte Ueckermann

Platinum group

Norite

10.1007/s00126-020-00998-2

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Citations (10)

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

Mineralium Deposita (2024)

Ben Hayes Reza Maghdour‐Mashhour Lewis D. Ashwal Albertus J.B. Smith Henriëtte Ueckermann

Abstract 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 87 Sr/ 86 Sr i (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 87 Sr/ 86 Sr i 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.

Infiltration (HVAC)

10.1007/s00126-024-01278-z

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