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Malte Junge
Institut für Geo- und Umweltwissenschaften Mineralogie-Petrologie, Universität Freiburg, Alberstr.23b, 79104 Freiburg, Germany

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Journal article
Published: 25 June 2020 in Minerals
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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 (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.

ACS Style

Reiner Klemd; Andreas Beinlich; Matti Kern; Malte Junge; Laure Martin; Marcel Regelous; Robert Schouwstra. Magmatic PGE Sulphide Mineralization in Clinopyroxenite from the Platreef, Bushveld Complex, South Africa. Minerals 2020, 10, 570 .

AMA Style

Reiner Klemd, Andreas Beinlich, Matti Kern, Malte Junge, Laure Martin, Marcel Regelous, Robert Schouwstra. Magmatic PGE Sulphide Mineralization in Clinopyroxenite from the Platreef, Bushveld Complex, South Africa. Minerals. 2020; 10 (6):570.

Chicago/Turabian Style

Reiner Klemd; Andreas Beinlich; Matti Kern; Malte Junge; Laure Martin; Marcel Regelous; Robert Schouwstra. 2020. "Magmatic PGE Sulphide Mineralization in Clinopyroxenite from the Platreef, Bushveld Complex, South Africa." Minerals 10, no. 6: 570.

Review
Published: 10 December 2019 in Minerals
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Several deposits of low-sulfide Pt–Pd ores have been discovered in recent decades in the Paleoproterozoic Fedorova–Pana Layered Complex located in the Kola Region (Murmansk Oblast) of Russia. The deposits are divided into two types: reef-style, associated with the layered central portions of intrusions, and contact-style, localized in the lower parts of intrusions near the contact with the Archean basement. The Kievey and the North Kamennik deposits represent the first ore type and are confined to the North PGE Reef located 600–800 m above the base of the West Pana Intrusion. The reef is associated with a horizon of cyclically interlayered orthopyroxenite, gabbronorite and anorthosite. The average contents of Au, Pt and Pd in the Kievey ore are 0.15, 0.53 and 3.32 ppm, respectively. The North Kamennik deposit has similar contents of noble metals. The Fedorova Tundra deposit belongs to the second ore type and has been explored in two sites in the lower part of the Fedorova intrusion. Mineralization is mainly associated mainly with taxitic or varied-textured gabbronorites, forming a matrix of intrusive breccia with fragments of barren orthopyroxenite. The ores contain an average of 0.08 ppm Au, 0.29 ppm Pt and 1.20 ppm Pd. In terms of PGE resources, the Fedorova Tundra is the largest deposit in Europe, hosting more than 300 tons of noble metals.

ACS Style

Nikolay Yu. Groshev; Tatyana V. Rundkvist; Bartosz T. Karykowski; Wolfgang D. Maier; Aleksey U. Korchagin; Anton N. Ivanov; Malte Junge. Low-Sulfide Platinum–Palladium Deposits of the Paleoproterozoic Fedorova–Pana Layered Complex, Kola Region, Russia. Minerals 2019, 9, 764 .

AMA Style

Nikolay Yu. Groshev, Tatyana V. Rundkvist, Bartosz T. Karykowski, Wolfgang D. Maier, Aleksey U. Korchagin, Anton N. Ivanov, Malte Junge. Low-Sulfide Platinum–Palladium Deposits of the Paleoproterozoic Fedorova–Pana Layered Complex, Kola Region, Russia. Minerals. 2019; 9 (12):764.

Chicago/Turabian Style

Nikolay Yu. Groshev; Tatyana V. Rundkvist; Bartosz T. Karykowski; Wolfgang D. Maier; Aleksey U. Korchagin; Anton N. Ivanov; Malte Junge. 2019. "Low-Sulfide Platinum–Palladium Deposits of the Paleoproterozoic Fedorova–Pana Layered Complex, Kola Region, Russia." Minerals 9, no. 12: 764.

Article
Published: 27 October 2018 in Mineralium Deposita
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The Platreef of the Bushveld Complex is currently the largest PGE open pit deposit. In order to investigate the behavior of PGE during weathering, three boreholes covering a sequence of oxidized and pristine Platreef ore from the Mogalakwena mine were studied. Further, sulfides and platinum-group minerals (PGM) at various locations along the strike of the Platreef, at Townlands, Tweefontein and Nonnenwerth were compared to those of the Mogalakwena mine (Overysel, Sandsloot). In the pristine ore, PGE generally occur as PGM, or in solid solution within sulfides. PGM are usually associated with sulfide and mainly comprise (Pt,Pd)-bismuthotellurides, cooperite-braggite, and sperrylite. Electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) indicate concentrations of Pd in pentlandite (up to 185 ppm), whereas pyrrhotite contains up to 15 ppm of Os, Ir, and Ru, and chalcopyrite is usually devoid of PGE. Two compositionally different groups of pyrite differing in Ni, Co, and Pt contents were identified. Sulfur isotope data indicate different degrees of assimilation from the country rocks. Near-surface, oxidized PGE ores have a large economic potential. However, attempts to extract the PGE have proven unfeasible due to low PGE recoveries (< 30%) achieved by conventional metallurgical methods. In the oxidized ores, rare relict PGM are present. EPMA and LA-ICP-MS measurements demonstrated that secondary iron oxides/hydroxides and secondary silicates contain erratically distributed concentrations of Rh, Pt, and Pd (up to several 100 ppm). The polymodal distribution of PGE in the weathered PGE ores explains the low recovery rates by conventional flotation processing.

ACS Style

Malte Junge; Thomas Oberthür; Dennis Kraemer; Frank Melcher; Ruben Piña; Insa T. Derrey; Tawanda Manyeruke; Harald Strauss. Distribution of platinum-group elements in pristine and near-surface oxidized Platreef ore and the variation along strike, northern Bushveld Complex, South Africa. Mineralium Deposita 2018, 54, 885 -912.

AMA Style

Malte Junge, Thomas Oberthür, Dennis Kraemer, Frank Melcher, Ruben Piña, Insa T. Derrey, Tawanda Manyeruke, Harald Strauss. Distribution of platinum-group elements in pristine and near-surface oxidized Platreef ore and the variation along strike, northern Bushveld Complex, South Africa. Mineralium Deposita. 2018; 54 (6):885-912.

Chicago/Turabian Style

Malte Junge; Thomas Oberthür; Dennis Kraemer; Frank Melcher; Ruben Piña; Insa T. Derrey; Tawanda Manyeruke; Harald Strauss. 2018. "Distribution of platinum-group elements in pristine and near-surface oxidized Platreef ore and the variation along strike, northern Bushveld Complex, South Africa." Mineralium Deposita 54, no. 6: 885-912.

Journal article
Published: 01 December 2017 in South African Journal of Geology
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Weathered chromitite layers from the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex in South Africa are mined for chromite but have the potential to be processed for platinum-group elements (PGE) as a by-product. However, recovery rates of PGE from weathered PGE ores are apparently low because of the supergene redistribution of PGE. Thus, understanding the processes that are responsible for PGE mobilization during weathering processes is useful to assess the PGE potential in weathered chromitites. In this study the distribution of platinum (Pt) and palladium (Pd) in soil samples from the LG and MG chromitites of the Thaba Mine (western Bushveld Complex) is investigated, with a special focus on the influence of organic matter on Pt and Pd mobilization. For this purpose, the soil samples were treated with different chemical digestion methods (aqua regia digestion and total digestion), and the Pt and Pd concentrations in humic and fulvic acids extracted from the soils were determined. The average total Pt and Pd concentrations of the soil samples (integrated over the whole soil horizons) are up to 62 ng/g and 128 ng/g, respectively, and their concentrations increase towards the topsoil. The humic acid extracts contain up to 0.04 ng/g Pt and up to 6.78 ng/g Pd and the fulvic acid extracts contain up to 0.16 ng/g Pt and up to 2.72 ng/g Pd. Up to 1% of the total Pt present in the soil is bound to fulvic acids, whereas up to 7% Pd is bound to humic acids. Palladium is mobilized equally by humic and fulvic acids, whereas the transport of Pt occurs preferentially by fulvic acids, indicating a higher mobility of Pd compared to Pt under supergene conditions during soil formation.

ACS Style

L. Oppermann; M. Junge; S. Schuth; F. Holtz; U. Schwarz-Schampera; L. Sauheitl. Mobility and distribution of palladium and platinum in soils above Lower and Middle Group chromitites of the western Bushveld Complex, South Africa. South African Journal of Geology 2017, 120, 511 -524.

AMA Style

L. Oppermann, M. Junge, S. Schuth, F. Holtz, U. Schwarz-Schampera, L. Sauheitl. Mobility and distribution of palladium and platinum in soils above Lower and Middle Group chromitites of the western Bushveld Complex, South Africa. South African Journal of Geology. 2017; 120 (4):511-524.

Chicago/Turabian Style

L. Oppermann; M. Junge; S. Schuth; F. Holtz; U. Schwarz-Schampera; L. Sauheitl. 2017. "Mobility and distribution of palladium and platinum in soils above Lower and Middle Group chromitites of the western Bushveld Complex, South Africa." South African Journal of Geology 120, no. 4: 511-524.

Journal article
Published: 01 February 2017 in American Mineralogist
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Synthetic fluid inclusions formed in high P-T experiments, which are subsequently analyzed with LA-ICP-MS, enable us to collect thermodynamic data to constrain metal transport in aqueous fluids as well as partitioning of metals between coexisting phases. The most essential prerequisite for such studies is to ensure that equilibrium conditions between liquid and solid phases are reached prior to the formation of synthetic fluid inclusions in the host mineral. Various methods have been proposed by different authors to achieve this goal, but to this point our knowledge on the best approach to synthesize equilibrated fluid inclusions under constrained pressure, temperature, and compositional (P, T, and X) conditions remains poor. In addition, information on the time needed to reach equilibrium metal concentrations in the fluid as well as on the timing of the onset of fluid inclusion formation in the host mineral are scarce. The latter has been tested in a series of time-dependent experiments at 800 °C and 200 MPa using scheelite (CaWO4), molybdenite (MoS2) and metallic gold as dissolving phases and using different approaches to optimize the formation of equilibrated fluid inclusions. Both and were fixed during all experiments using the pyrite-pyrrhotite-magnetite buffer (PPM). As an intermediate in situ quenching of the sample charge plays an important role in the synthesis of fluid inclusions, we further tested the efficiency of such an intermediate quench for re-opening fluid inclusions formed at 600 °C and 200 MPa. Our results reveal that fluid inclusions start forming almost instantaneously and that equilibrium between fluid and solid phases occurs in the timescale of less than two hours for molybdenite and gold up to ca. 10 h for scheelite. The best approach to synthesize equilibrated fluid inclusions at 800 °C was obtained by using an intermediate quench on a previously unfractured quartz host. Experiments at 600 °C showed similar results and illustrate that this should be the method of choice down to this temperature. Below 600 °C pre-treatment of the quartz host (HF etching and/or thermal fracturing) becomes important to produce large enough fluid inclusions for the analyses via LA-ICP-MS and special care must be taken to prevent premature entrapment of the fluid. Fluids with 8 wt% NaCl in equilibrium with scheelite, molybdenite and gold at 800 °C and 200 MPa have concentrations of ca. 7300 ppm W, 1300 ppm Mo, and 300 ppm Au, respectively, which is in good agreement with results from other studies or extrapolation from lower temperatures. It can be concluded that the formation of synthetic fluid inclusions from an equilibrated fluid is possible, but different experimental designs are required, depending on the investigated temperature. In general, dissolution of solid phases seems to be much faster than previously assumed, so that experimental run durations can be designed considerably shorter, which is of great advantage when using fast-consuming mineral buffers.

ACS Style

Insa T. Derrey; Evgeniya Dupliy; Roman E. Botcharnikov; Ingo Horn; Malte Junge; Stefan Weyer; Moritz Albrecht; François Holtz. Experimental tests on achieving equilibrium in synthetic fluid inclusions: Results for scheelite, molybdenite, and gold solubility at 800 °C and 200 MPa. American Mineralogist 2017, 102, 275 -283.

AMA Style

Insa T. Derrey, Evgeniya Dupliy, Roman E. Botcharnikov, Ingo Horn, Malte Junge, Stefan Weyer, Moritz Albrecht, François Holtz. Experimental tests on achieving equilibrium in synthetic fluid inclusions: Results for scheelite, molybdenite, and gold solubility at 800 °C and 200 MPa. American Mineralogist. 2017; 102 (2):275-283.

Chicago/Turabian Style

Insa T. Derrey; Evgeniya Dupliy; Roman E. Botcharnikov; Ingo Horn; Malte Junge; Stefan Weyer; Moritz Albrecht; François Holtz. 2017. "Experimental tests on achieving equilibrium in synthetic fluid inclusions: Results for scheelite, molybdenite, and gold solubility at 800 °C and 200 MPa." American Mineralogist 102, no. 2: 275-283.

Letter
Published: 18 August 2016 in Mineralium Deposita
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The chromitites of the Bushveld Complex in South Africa contain vast resources of platinum-group elements (PGE). However, knowledge of the distribution and the mineralogical siting of the PGE in the lower group (LG) and middle group (MG) chromitite seams of the Bushveld Complex is limited. We studied concentrates from the LG-6 and MG-2 chromitites of the western Bushveld Complex by a variety of microanalytical techniques. The dominant PGM are sulfides, namely laurite, cooperite-braggite, and malanite-cuprorhodsite, followed by PGE-sulfarsenides, sperrylite, and Pt-Fe alloys. Laurite is the most abundant PGM (vol%). The matching sets of PGM present in the LG and MG chromitites of both the western and the eastern Bushveld Complex, and in the UG-2 chromitite, show strong similarities which support the assumption of a characteristic and general chromitite-related PGM assemblage. Palladium and Rh contents in pentlandite are low and erratic although maximum contents of 7730 ppm Pd and 6020 ppm Rh were detected. Rare thiospinels of the polydymite-linnaeite-greigite series have PGE contents of 1430 ppm Pt, 5370 ppm Rh, and 1460 ppm Pd. The various PGE occur in different deportment: Platinum is generally present in the form of discrete PGM (sulfides, arsenides, alloys). Palladium is present as a large variety of discrete PGM and also incorporated in pentlandite. Rhodium forms discrete PGM and is occasionally present in pentlandite. The IPGE (Os, Ir, and Ru) are dominantly incorporated in laurite (often as inclusions in chromite) and also occur as sulfarsenides.

ACS Style

Malte Junge; Thomas Oberthür; Inga Osbahr; Paul Gutter. Platinum-group elements and minerals in the lower and middle group chromitites of the western Bushveld Complex, South Africa. Mineralium Deposita 2016, 51, 841 -852.

AMA Style

Malte Junge, Thomas Oberthür, Inga Osbahr, Paul Gutter. Platinum-group elements and minerals in the lower and middle group chromitites of the western Bushveld Complex, South Africa. Mineralium Deposita. 2016; 51 (7):841-852.

Chicago/Turabian Style

Malte Junge; Thomas Oberthür; Inga Osbahr; Paul Gutter. 2016. "Platinum-group elements and minerals in the lower and middle group chromitites of the western Bushveld Complex, South Africa." Mineralium Deposita 51, no. 7: 841-852.

Journal article
Published: 28 October 2014 in Mineralium Deposita
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The Bushveld Complex in South Africa hosts the world’s largest resources of platinum-group elements (PGEs), which are mainly mined from three ore bodies, namely the Merensky Reef, the UG-2 chromitite, and the Platreef. In these ores, the PGEs are bimodally distributed, occurring both as discrete platinum-group minerals (PGMs) and hosted by sulfides. The presence of PGEs in sulfides has been demonstrated by electron probe microanalysis, laser ablation induced coupled plasma mass spectrometry, secondary ion mass spectrometry, and particle-induced X-ray emission. However, evidence is lacking on the mineralogical siting of the PGEs, e.g., whether they occur in solid solution, as nano-inclusions, and/or micro-inclusions. Therefore, in the present study, a combination of focused ion beam and transmission electron microscopy was used which allows to obtain crystal structural relationships between the host mineral and incorporated trace elements and revealing the physicochemical state of the PGE in sulfides. The present study confirms the existence of micrometer-sized discrete PGMs in the ores. Further, the PGEs occur in a number of forms, namely (1) as discrete nano-inclusions of PGMs, (2) as patchily distributed solid solution, (3) ordered within the pentlandite crystal structure, substituting for Ni and/or Fe (superlattice), and (4) as homogenous solid solution. Nanometer-sized PGMs (nPGMs) show no orientation relationship with the host sulfide mineral. Consequently, they are discrete phases, which were trapped within pentlandite during sulfide growth. Heterogeneous and patchy distributions of Rh and Ir within the pentlandite lattice suggest that Rh and Ir were already present within the sulfide liquid. The absence of possible reaction partners (e.g., Bi, As, and Sn) necessary for the formation of discrete PGMs forced Rh and Ir to remain in the crystal lattice of pentlandite and down-temperature exsolution caused patchy distribution patterns of Rh and Ir. High concentrations of Rh and Ir in pentlandite initiate ordering of the randomly distributed PGE in form of nanometer-sized lamellae resulting in the formation of a superlattice. Palladium is homogenously distributed within the pentlandite lattice, even at high Pd concentrations, and in addition also occurs as nPGMs.

ACS Style

Malte Junge; Richard Wirth; Thomas Oberthür; Frank Melcher; Anja Schreiber. Mineralogical siting of platinum-group elements in pentlandite from the Bushveld Complex, South Africa. Mineralium Deposita 2014, 50, 41 -54.

AMA Style

Malte Junge, Richard Wirth, Thomas Oberthür, Frank Melcher, Anja Schreiber. Mineralogical siting of platinum-group elements in pentlandite from the Bushveld Complex, South Africa. Mineralium Deposita. 2014; 50 (1):41-54.

Chicago/Turabian Style

Malte Junge; Richard Wirth; Thomas Oberthür; Frank Melcher; Anja Schreiber. 2014. "Mineralogical siting of platinum-group elements in pentlandite from the Bushveld Complex, South Africa." Mineralium Deposita 50, no. 1: 41-54.

Journal article
Published: 06 February 2014 in Economic Geology
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The UG-2 chromitite of the Bushveld Complex in South Africa contains the world’s largest resources of platinum group elements (PGEs). However, only limited work has been conducted on the fine-scale chemical variation of chromite, and the distribution of PGEs and platinum group minerals (PGMs) within the UG-2. In the present study, one drill core (155 cm long) covering the sequence of the UG-2 chromitite at the Karee mine in the western Bushveld Complex was studied in detail.

ACS Style

Malte Junge; Thomas Oberthür; Frank Melcher. CRYPTIC VARIATION OF CHROMITE CHEMISTRY, PLATINUM GROUP ELEMENT AND PLATINUM GROUP MINERAL DISTRIBUTION IN THE UG-2 CHROMITITE: AN EXAMPLE FROM THE KAREE MINE, WESTERN BUSHVELD COMPLEX, SOUTH AFRICA. Economic Geology 2014, 109, 795 -810.

AMA Style

Malte Junge, Thomas Oberthür, Frank Melcher. CRYPTIC VARIATION OF CHROMITE CHEMISTRY, PLATINUM GROUP ELEMENT AND PLATINUM GROUP MINERAL DISTRIBUTION IN THE UG-2 CHROMITITE: AN EXAMPLE FROM THE KAREE MINE, WESTERN BUSHVELD COMPLEX, SOUTH AFRICA. Economic Geology. 2014; 109 (3):795-810.

Chicago/Turabian Style

Malte Junge; Thomas Oberthür; Frank Melcher. 2014. "CRYPTIC VARIATION OF CHROMITE CHEMISTRY, PLATINUM GROUP ELEMENT AND PLATINUM GROUP MINERAL DISTRIBUTION IN THE UG-2 CHROMITITE: AN EXAMPLE FROM THE KAREE MINE, WESTERN BUSHVELD COMPLEX, SOUTH AFRICA." Economic Geology 109, no. 3: 795-810.