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1
O’Connor, Cyril, e Tatiana Alexandrova. "The Geological Occurrence, Mineralogy, and Processing by Flotation of Platinum Group Minerals (PGMs) in South Africa and Russia". Minerals 11, n. 1 (7 gennaio 2021): 54. http://dx.doi.org/10.3390/min11010054.
Testo completoAbstract (sommario):
Russia and South Africa are the world’s leading producers of platinum group elements (PGEs). This places them in a unique position regarding the supply of these two key industrial commodities. The purpose of this paper is to provide a comparative high-level overview of aspects of the geological occurrence, mineralogy, and processing by flotation of the platinum group minerals (PGMs) found in each country. A summary of some of the major challenges faced in each country in terms of the concentration of the ores by flotation is presented alongside the opportunities that exist to increase the production of the respective metals. These include the more efficient recovery of minerals such as arsenides and tellurides, the management of siliceous gangue and chromite in the processing of these ores, and, especially in Russia, the development of novel processing routes to recover PGEs from relatively low grade ores occurring in dunites, black shale ores and in vanadium-iron-titanium-sulphide oxide formations.
2
Varentsov, I. M., e V. N. Kuleshov. "Rare Elements—Markers of the Formation Setting of Manganese and Iron Ores in the Kalahari and Postmasburg Manganese Fields (South Africa): Communication 2. Postmasburg Iron and Manganese Field". Lithology and Mineral Resources 54, n. 5 (settembre 2019): 412–28. http://dx.doi.org/10.1134/s0024490219050067.
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Long, Fang Yi, Sheng Li Wu, Juan Zhu, Yuan Du e Guo Liang Zhang. "Experimental Research on Bonding Intensity of Iron Ores in the Sintering Process". Advanced Materials Research 391-392 (dicembre 2011): 60–64. http://dx.doi.org/10.4028/www.scientific.net/amr.391-392.60.
Testo completoAbstract (sommario):
The bonding intensity of four kinds of ores from Brazil, Australia and South Africa is researched in this study, and the influence factors are analyzed. The results show that, the ores of different types have apparently differences in bonding intensity, ores from Brazil and South Africa have high bonding intensity, while ores from Australia have low bonding intensity; The foundation of generation of effective liquid is adequate liquid phase fluidity and the lower porosity of core ore; The ratio of porosity of core ore and the index of liquid phase fluidity has negative correlation with the bonding intensity.
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O’Connor, Cyril, e Tatiana Alexandrova. "The Geological Occurrence, Mineralogy, and Processing by Flotation of Platinum Group Minerals (PGMs) in South Africa and Russia". Minerals 11, n. 1 (7 gennaio 2021): 54. http://dx.doi.org/10.3390/min11010054.
Testo completoAbstract (sommario):
Russia and South Africa are the world’s leading producers of platinum group elements (PGEs). This places them in a unique position regarding the supply of these two key industrial commodities. The purpose of this paper is to provide a comparative high-level overview of aspects of the geological occurrence, mineralogy, and processing by flotation of the platinum group minerals (PGMs) found in each country. A summary of some of the major challenges faced in each country in terms of the concentration of the ores by flotation is presented alongside the opportunities that exist to increase the production of the respective metals. These include the more efficient recovery of minerals such as arsenides and tellurides, the management of siliceous gangue and chromite in the processing of these ores, and, especially in Russia, the development of novel processing routes to recover PGEs from relatively low grade ores occurring in dunites, black shale ores and in vanadium-iron-titanium-sulphide oxide formations.
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Varentsov, I. M., e V. N. Kuleshov. "Rare elements — setting markers of the formation of the manganese and iron ore deposits of Kalahari and Postmasburg areas (South Africa). Communication 2. Iron- and manganese ore of Postmasburg area". Литология и полезные ископаемые, n. 5 (20 ottobre 2019): 466–85. http://dx.doi.org/10.31857/s0024-497x20195466-485.
Testo completoAbstract (sommario):
In the world resources of manganese and iron ores, a significant place belongs to the Postmasburg ore field (South Africa), enclosed in rocks of the Transvaal Supegroup. Ore deposits have the nature of karst residual accumulations. A number of elements (B, Cr, Ni, Zn, Ge, As, Se, Mo, Ag, Cd, Sb, Te, W, Pb, REE) form a characteristic association that sheds light on the geochemistry of the ore formation processes. Of these, the most representative elements are: Mo, As, Ag and REE. Molybdenum is distinguished by the chemisorption incorporation nature of accumulation in the ores under consideration, often with the formation of epic growths of ferri molybdate-type minerals. Arsenic leached from substrate rocks and accumulated in karstic Mn-Fe- and Fe-ores reflects the total effect of the dominant iron oxide minerals on its mobility. The behavior of silver is controlled by the processes of hypergenic change of Archean-Early Proterozoic carbonate rocks and banded iron ores (BIF). Comparison of the distribution of REE in karst Fe-, Mn-Fe- and Mn-ores and in banded iron ores shows that they are characterized by similar values of cerium (C/Ce*) and europium (Eu/Eu*) anomalies, but differ in the fractionation of heavy and light REE (typical values: Ce/Ce* = 0.7‒1.0; Eu/Eu* = 0.8‒1.1). Strip iron ores and associated manganese ore deposits accumulated in the marginal anoxide-disoxide marine basin, which was limited to continental land. Anoxide and disoxide conditions were the result of intense hydrothermal activity.
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Gutzmer, J., e N. J. Beukes. "Mineralogy and mineral chemistry of oxide-facies manganese ores of the Postmasburg manganese field, South Africa". Mineralogical Magazine 61, n. 405 (aprile 1997): 213–31. http://dx.doi.org/10.1180/minmag.1997.061.405.05.
Testo completoAbstract (sommario):
AbstractThe diagenetic to very low-grade metamorphic manganese ores of the Postmasburg manganese field provide a unique example of oxide-facies manganese ores in a Palaeoproterozoic palaeokarst setting. The ores are composed mainly of braunite group minerals, including braunite, partridgeite and bixbyite, with rare braunite II and Ca-poor, silica-depleted braunite. Iron-poor partridgeite is distinguished from Fe-rich bixbyite and the occurrence of Ca-poor, silica-depleted braunite is reported for the first time. Braunite and partridgeite formed during early diagenesis but remained stable under greenschist facies metamorphic conditions. In contrast, bixbyite is apparently a product of metasomatic remobilisation under peak metamorphic conditions. It is suggested that local variations of the metamorphic mineral association reflect variations of the host rock composition and that they are not related to changing P-T conditions of metamorphic alteration, a model promoted by previous authors. The phase chemistry of braunite, braunite II and bixbyite is explained by the existing polysomatic stacking model for the braunite group. However, the chemical composition of partridgeite and Ca-poor, silica-depleted braunite can only be explained by introducing a distinct module layer, with partridgeite composition, to the existing polysomatic stacking model.
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Evdokimov, Aleksandr, e Benedict Pharoe. "Features of the mineral and chemical composition of the Northwest manganese ore occurrence in the Highveld region, South Africa". Journal of Mining Institute 248 (25 maggio 2021): 195–208. http://dx.doi.org/10.31897/pmi.2021.2.4.
Testo completoAbstract (sommario):
The Northwest manganese ore mineralisation is located at a relative distance from traditionally known manganese mining areas in a new manganese-bearing region (Highveld) in the Northwest Province, Republic of South Africa. The ore occurrence was studied on farms: Buchansvale 61 IQ, Weltevreden 517 JQ, Rhenosterhoek 343 JP and Kafferskraal 306 JP. The data obtained from studying the geology of the area pointed out to interests regarding the development criterias for search of similar ore mineralisations in the northwest region of South Africa. The ore occurs predominantly in the form of powdered manganese wad, manganese nodules and crusts, confined to the karstic structures of the upper section of the dolomites. X-ray powder diffraction (XRD), Scanning electron microscopy with energy dispersive link (SEM-EDS) and X-ray fluorescence were utilized to unveil the mineral and chemical composition of the ore samples. The present study therefore presents the results on both chemical and mineral composition of manganese ores, and their depth and longitudinal distribution. Karstic areas causing an increased local thickness of the ore body were identified. The geochemical and microspcopic study of the ores indicates their supergene nature. The main ore minerals includes cryptomelane, lithiophorite, purolusite, hollandite and romanechite associated with impurity components of Ba, Ce, Co, La, Cr, Zn and V.
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Bandama, Foreman, Shadreck Chirikure e Simon Hall. "Ores Sources, Smelters and Archaeometallurgy: Exploring Iron Age Metal Production in the Southern Waterberg, South Africa". Journal of African Archaeology 11, n. 2 (11 novembre 2013): 243–67. http://dx.doi.org/10.3213/2191-5784-10240.
Testo completoAbstract (sommario):
The Southern Waterberg in Limpopo Province is archaeologically rich, especially when it comes to evidence of pre-colonial mining and metal working. Geologically, the area hosts important mineral resources such as copper, tin and iron which were smelted by agriculturalists in the precolonial period. In this region however, tin seems to be the major attraction given that Rooiberg is still the only source of cassiterite in southern Africa to have provided evidence of mining before European colonization. This paper reports the results of archaeological and archaeometallurgical work which was carried out in order to reconstruct the technology of metalworking as well as the cultural interaction in the study area and beyond. The ceramic evidence shows that from the Eiland Phase (1000–1300 AD) onwards there was cross borrowing of characteristic decorative traits amongst extant groups that later on culminated in the creation of a new ceramic group known as Rooiberg. In terms of mining and metal working, XRF and SEM analyses, when coupled with optical microscopy, indicate the use of indigenous bloomery techniques that are widespread in pre-colonial southern Africa. Tin and bronze production was also represented and their production remains also pin down this metallurgy to particular sites and excludes the possibility of importing of finished tin and bronze objects into this area.
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Fairey, Brenton J., Martin J. Timmerman, Masafumi Sudo e Harilaos Tsikos. "The Role of Hydrothermal Activity in the Formation of Karst-Hosted Manganese Deposits of the Postmasburg Mn Field, Northern Cape Province, South Africa". Minerals 9, n. 7 (3 luglio 2019): 408. http://dx.doi.org/10.3390/min9070408.
Testo completoAbstract (sommario):
The Postmasburg Manganese Field (PMF), Northern Cape Province, South Africa, once represented one of the largest sources of manganese ore worldwide. Two belts of manganese ore deposits have been distinguished in the PMF, namely the Western Belt of ferruginous manganese ores and the Eastern Belt of siliceous manganese ores. Prevailing models of ore formation in these two belts invoke karstification of manganese-rich dolomites and residual accumulation of manganese wad which later underwent diagenetic and low-grade metamorphic processes. For the most part, the role of hydrothermal processes and metasomatic alteration towards ore formation has not been adequately discussed. Here we report an abundance of common and some rare Al-, Na-, K- and Ba-bearing minerals, particularly aegirine, albite, microcline, banalsite, sérandite-pectolite, paragonite and natrolite in Mn ores of the PMF, indicative of hydrothermal influence. Enrichments in Na, K and/or Ba in the ores are generally on a percentage level for most samples analysed through bulk-rock techniques. The presence of As-rich tokyoite also suggests the presence of As and V in the hydrothermal fluid. The fluid was likely oxidized and alkaline in nature, akin to a mature basinal brine. Various replacement textures, particularly of Na- and K- rich minerals by Ba-bearing phases, suggest sequential deposition of gangue as well as ore-minerals from the hydrothermal fluid, with Ba phases being deposited at a later stage. The stratigraphic variability of the studied ores and their deviation from the strict classification of ferruginous and siliceous ores in the literature, suggests that a re-evaluation of genetic models is warranted. New Ar-Ar ages for K-feldspars suggest a late Neoproterozoic timing for hydrothermal activity. This corroborates previous geochronological evidence for regional hydrothermal activity that affected Mn ores at the PMF but also, possibly, the high-grade Mn ores of the Kalahari Manganese Field to the north. A revised, all-encompassing model for the development of the manganese deposits of the PMF is then proposed, whereby the source of metals is attributed to underlying carbonate rocks beyond the Reivilo Formation of the Campbellrand Subgroup. The main process by which metals are primarily accumulated is attributed to karstification of the dolomitic substrate. The overlying Asbestos Hills Subgroup banded iron formation (BIF) is suggested as a potential source of alkali metals, which also provides a mechanism for leaching of these BIFs to form high-grade residual iron ore deposits.
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Hicks, N., e D. J. C. Gold. "Lithostratigraphy of the Sinqeni Formation, Pongola Supergroup, South Africa". South African Journal of Geology 123, n. 3 (1 settembre 2020): 399–420. http://dx.doi.org/10.25131/sajg.123.0027.
Testo completoAbstract (sommario):
Abstract The Mesoarchaean Sinqeni Formation forms the lowermost unit of the predominantly sedimentary Mozaan Group (Pongola Supergroup) of southern Africa. The formation comprises a dominantly arenaceous succession, which can be subdivided into four members. A laterally discontinuous gold- and uranium-bearing conglomerate package (Denny Dalton Member) is commonly developed at the base of the formation. Overlying the basal conglomerates are two significant quartz arenite packages (Dipka, and Kwaaiman Members) which are separated by a ferruginous shale package (Vlakhoek Member) that locally hosts banded-iron formation. The formation is the most extensively exposed succession of the Mozaan Group, cropping out extensively in the Hartland region, as well as in multiple inliers from Amsterdam in the Mpumalanga to Nkandla in central KwaZulu-Natal, with further exposures in Eswatini. Subeconomic gold and uranium mineralisation occur sporadically within the conglomerates of the Denny Dalton Member, and have previously been mined from multiple occurrences in the White Mfolozi, Mhlatuze and Nkandla Inliers whilst many prospecting trenches are found in the conglomerates of the Hartland and Amsterdam areas. Gold has also briefly been exploited from ferruginous shales and iron formations of the Vlakhoek Member in the Altona area. Litho-correlative equivalents of the formation comprise the Mandeva Formation (White Mfolozi Inlier), Skurwerant Formation (Amsterdam region) and Mkaya Formation (Magudu region).
11
MAIER, W. D., M. A. G. ANDREOLI, D. I. GROVES e S. J. BARNES. "PETROGENESIS OF CU-NI SULPHIDE ORES FROM O'OKIEP AND KLIPRAND, NAMAQUALAND, SOUTH AFRICA: CONSTRAINTS FROM CHALCOPHILE METAL CONTENTS". South African Journal of Geology 115, n. 4 (1 dicembre 2012): 499–514. http://dx.doi.org/10.2113/gssajg.115.4.499.
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Kou, Caihua, Zhaochong Zhang, M. Santosh, He Huang e Jiang Zhu. "Oldest volcanic-hosted submarine iron ores in South China: Evidence from zircon U–Pb geochronology and geochemistry of the Paleoproterozoic Dahongshan iron deposit". Gondwana Research 49 (settembre 2017): 182–204. http://dx.doi.org/10.1016/j.gr.2017.05.016.
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Channer, Dominic, Elsa Graffe e Pedro Vielma. "Geology, Mining, and Mineral Potential of Southern Venezuela". SEG Discovery, n. 62 (1 luglio 2005): 5–22. http://dx.doi.org/10.5382/segnews.2005-62.fea.
Testo completoAbstract (sommario):
ABSTRACT The highly prospective Precambrian Guyana shield south of the Orinoco River in Venezuela can be divided into five main provinces: Imataca, Pastora-Botanamo, Cuchivero, Amazonas, and Roraima. The combination of gold-rich granite-greenstone belts, felsic volcanic and granitic terrains, highly diamondiferous kimberlites, widespread gold and diamond placers, and large unexplored areas makes this region an exciting exploration province. Important mineralization events occurred at different times over a wide range of geologic time, from 3.2 Ga for banded iron formation in Imataca, 2.0 to 1.9 Ga for gold mineralization in Pastora-Botanamo, 0.71 Ga for diamondiferous kimberlite emplacement in Cuchivero, and the Tertiary for formation of enriched iron ores and bauxite ores in Imataca and Amazonas. Iron and aluminum mining is controlled by state mining corporations, with current annual ore production of 23 and 5.2 Mt, respectively. Gold mining is divided between state and private companies and artisanal operations. Total gold production is probably about 750,000 oz per year, including artisanal production. All diamond production is currently artisanal, with total estimated annual production of 500,000 ct. When current project go into production, Venezuela’s gold and diamond production will pass 1.3 Moz/yr and 1 Mct/yr, respectively. Artisanal mining is a key part of the gold and diamond-mining industry in Venezuela, and prospective exploration and mining companies must be aware of this; they should include projects with artisanal miners and local communities in their exploration and development planning.
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Gutzmmer, J., N. J. Beukes, A. S. E. Kleyenstuber e A. M. Burger. "Magnetic hausmannite from hydrothermally altered manganese ore in the Palaeoproterozoic Kalahari manganese deposit, Transvaal Supergroup, South Africa". Mineralogical Magazine 59, n. 397 (dicembre 1995): 703–16. http://dx.doi.org/10.1180/minmag.1995.059.397.12.
Testo completoAbstract (sommario):
AbstractHausmannite (Mn3O4), a manganese oxide with a tetragonally distorted spinel structure, is considered to be ferrimagnetic with a very low Curie temperature of 42.5 K. However, strongly magnetic hausmannite has been discovered in some of the hydrothermally altered high-grade manganese ores of the giant Kalahari manganese deposit in South Africa. EDS-electron microprobe analyses indicate magnetic hausmannite to contain on average between 3 and 11.3 wt.% Fe2O3. In contrast non-magnetic hausmannite contains on average about 1–3 wt.% Fe2O3. X-ray powder diffraction analyses reveal small changes in cell dimensions of the magnetic hausmannite related to the high iron content. Mössbauer spectroscopy suggests that all iron is in the trivalent state. Optical microscopy and scanning electron microscopy (electron back-scatter imaging) proved the magnetic hausmannite to be homogeneous in composition, containing only a few minute inclusions of hematite. Magnetic blocking temperatures of the iron-rich hausmannite, approximating the Curie temperature, are of the order of 750 K. It is suggested that the ferrimagnetic state of hausmannite is stabilized and enhanced by replacement of Mn3+ by Fe3+.
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Varentsov, I. M., e V. N. Kuleshov. "Rare elements — setting markers of the formation of the manganese and iron ore deposits of Kalahari and Postmasburg areas (South Africa). Communication 1. Kalahari manganese field". Литология и полезные ископаемые, n. 4 (9 luglio 2019): 364–86. http://dx.doi.org/10.31857/s0024-497x20194364-386.
Testo completoAbstract (sommario):
In manganese ores of the Hotazel Formation (Transvaal supergroup) of the Lower Proterozoic, associated with banded ferrous silicites, high concentrations of a number of rare elements (B, Ge, W, Mo, Cr, Ni, Zn, Cd, Pb, Ag, Bi, As, Sb, Te, Se) were determined. High boron contents in oxide-carbonate ores (manganese lutites) are considered as a consequence of the concentration by chemsorbtion of this element on Mn-carbonates. It is proposed that as a result of hydrothermal transformations, a wide range of ore-forming (mainly Fe, Mn) and rare elements (including REE) was removed from the underlying andesite-basaltic hyaloclastite Ongeluk Formation In manganese ores and ferruginous silicites, typical values of cerium (Ce/Ce* 0.28–1.72) and europium (Eu/Eu* 0.57–16.31) anomalies were established, which may indicate that the initial sediments accumulated in the marginal shallow sea basin with a pronounced oxide surface water layer and close to anoxide conditions near the bottom. Metalliferous (Mn, Fe) sediments of a shallow water basin at different stages of lithogenesis were enriched with europium (positive Eu/Eu*), subjected to metasomatosis (with redistribution of manganese and the formation of manganese carbonates) and, subsequently, regional metamorphism (up to the stage of sericitic green schists).
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Aleksandrova, Tatyana, e Cyril О’Connor. "Processing of platinum group metal ores in Russia and South Africa: current state and prospects". Journal of Mining Institute 244 (30 luglio 2020): 462–73. http://dx.doi.org/10.31897/pmi.2020.4.9.
Testo completoAbstract (sommario):
The presented study is devoted to a comparative review of the mineral raw material base of platinum group metals (PGMs) and technologies of their processing in South Africa and Russia, the largest PGM producers. Mineralogical and geochemical classification and industrial value of iron-platinum and platinum-bearing deposits are presented in this work. The paper also reviews types of PGM ore body occurrences, ore processing methods (with a special focus on flotation processes), as well as difficulties encountered by enterprises at the processing stage, as they increase recovery of the valuable components. Data on mineralogical features of PGM deposits, including the distribution of elements in the ores, are provided. The main lines of research on mineralogical features and processing of raw materials of various genesis are identified and validated.
Sulfide deposits are found to be of the highest industrial value in both countries. Such unconventional PGM sources, as black shale, dunites, chromite, low-sulfide, chromium and titanomagnetite ores, anthropogenic raw materials, etc. are considered. The main lines of research that would bring into processing non-conventional metal sources are substantiated.
Analysis of new processing and metallurgical methods of PGM recovery from non-conventional and industrial raw materials is conducted; the review of existing processing technologies for platinum-bearing raw materials is carried out. Technologies that utilize modern equipment for ultrafine grinding are considered, as well as existing reagents for flotation recovery; evaluation of their selectivity in relation to platinum minerals is presented.
Basing on the analysis of main technological processes of PGM ore treatment, the most efficient schemes are identified, i.e.,gravity and flotation treatment with subsequent metallurgical processing.
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Bau, Höhndorf, Dulski e Beukes. "Sources of Rare-Earth Elements and Iron in Paleoproterozoic Iron-Formations from the Transvaal Supergroup, South Africa: Evidence from Neodymium Isotopes". Journal of Geology 105, n. 1 (1997): 121. http://dx.doi.org/10.2307/30079890.
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Bau, Michael, Axel Höhndorf, Peter Dulski e Nicolas J. Beukes. "Sources of Rare-Earth Elements and Iron in Paleoproterozoic Iron-Formations from the Transvaal Supergroup, South Africa: Evidence from Neodymium Isotopes". Journal of Geology 105, n. 1 (gennaio 1997): 121–29. http://dx.doi.org/10.1086/606152.
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Vearncombe, J. R. "Structure of veins in a gold–pyrite deposit in banded iron formation, Amalia greenstone belt, South Africa". Geological Magazine 123, n. 6 (novembre 1986): 601–9. http://dx.doi.org/10.1017/s0016756800024110.
Testo completoAbstract (sommario):
AbstractFibrous quartz veins in deformed banded iron formation of the Amalia greenstone belt, southwestern Transvaal, are spatially related to gold–pyrite mineralization in both wallrock and vein inclusions. Poles to quartz vein orientations show a general parallelism with mineral elongation and fold plunges of the principal deformation in the wallrock. Quartz vein fibres show a consistent anticlockwise rotation, late components being subparallel to the elongation lineation, suggesting veining was probably synchronous with the principal deformation. Antitaxial fibrous veins, which dominate the mineralized banded iron formation, formed by the process of crack–seal which channelled mineralizing fluids along the vein walls, increasing the potential for fluid–wallrock interaction. Gold mineralization in quartz veins occurs in wall-parallel slivers of banded iron formation which have been plucked off the vein wall during antitaxial fibre growth. Mineralization can be explained by a process of fluid–wallrock interaction with sulphidation and gold precipitation.
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Mkhatshwa, S. F., B. M. Guy, A. J. B. Smith e K. S. Viljoen. "A mineralogical perspective on the recovery of uranium from brannerite-rich ore at Cooke Section, West Rand Goldfield, South Africa". South African Journal of Geology 123, n. 4 (9 novembre 2020): 615–32. http://dx.doi.org/10.25131/sajg.123.0031.
Testo completoAbstract (sommario):
Abstract The recovery of uranium from quartz-pebble conglomerates of the Witwatersrand Basin is accomplished through sulphuric acid dissolution under oxidising conditions. At Cooke Section on the West Rand Goldfield, the extraction process has been plagued by low to moderate yields on the order of 40 to 75%, as opposed to a target recovery of 80%. This has been ascribed to the high abundance of brannerite in the ore, which has traditionally been more problematic to leach. In addition to brannerite, poor metallurgical recoveries may also be associated with processing inefficiencies related to comminution, residence time, acid dosage and leach temperature. In view of this, a range of ore samples (channel samples) were collected from four uranium-bearing conglomerate horizons at Cooke Section (the A1, A5, E9EC and UE1A reefs) for detailed mineralogical and metallurgical characterisation, involving automated mineralogical analysis, and laboratory-scale leach testwork. The mineralogical results show that the major uranium-bearing minerals of uraninite, coffinite and brannerite are fine-grained (~80% passing 32 micron) and exhibit high degrees of mineral exposure to the lixiviant (~99%). Despite these favourable attributes, the elemental deportment data indicate that brannerite accounts for approximately 43% of the combined uranium budget. Further inspection shows that brannerite can be subdivided into three compositional subtypes: uraniferous brannerite (~13% U deportment), brannerite (~25% U deportment) and titaniferous brannerite (~5% U deportment). Baseline laboratory leach tests, which replicated plant leach conditions of 30 kg/ton acid, 4 kg/t oxidant, 24 hour residence time and 60°C leach temperature, yielded elevated dissolutions between ~77% and ~96%, with a combined overall uranium recovery of ~94%. These results are not consistent with the low yields obtained at the processing plant, and suggest that the high level of uranium recovery can be attributed to the effective leaching of brannerite (most likely uraniferous brannerite and brannerite). In view of prevailing market conditions, variability tests were carried out on a representative bulk composite sample to investigate the potential to achieve similar yields under more cost-effective leaching conditions. In these tests, a single parameter was varied (e.g. acid dosage), while the remaining parameters remained at baseline conditions. The results demonstrate that uranium recoveries of ~80% can be achieved on Cooke Section ores at low acid dosages and high temperatures (18 kg/t, 60°C) or at moderate acid dosages and low temperatures (23 kg/t, 30°C). The associated reduction of input costs would represent a significant cost-saving for the Ezulwini gold and uranium recovery plant. It is concluded that the poor uranium yields encountered during commercial processing of the ore are most likely related to undiagnosed inefficiencies in the treatment plant, such as excessive acid consumption related to elevated temperatures/oxidant addition and/or insufficient leach residence times, especially when recirculating, continuous flow-through leaching systems are in use. The broader implication of this study is that uranium processing operations beyond Cooke Section may be able to optimise their process designs and reduce input costs by quantifying the different types of brannerite within their ores through automated mineralogical analyses. The present study thus demonstrates the value of a geometallurgical approach in enhancing the understanding of uranium recovery through acid leaching.
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Killick, David, e Duncan Miller. "Smelting of magnetite and magnetite–ilmenite iron ores in the northern Lowveld, South Africa, ca. 1000 CE to ca. 1880 CE". Journal of Archaeological Science 43 (marzo 2014): 239–55. http://dx.doi.org/10.1016/j.jas.2013.12.016.
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Simonson, Bruce M., Steven Goderis e Nicolas J. Beukes. "First detection of extraterrestrial material in ca. 2.49 Ga impact spherule layer in Kuruman Iron Formation, South Africa". Geology 43, n. 3 (marzo 2015): 251–54. http://dx.doi.org/10.1130/g36225.1.
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Cairncross, Bruce. "The Where of Mineral Names: Gamagarite, Gloucester Mine, Gamagara Hills, Postmasburg Manganese and Iron-Ore Field, South Africa". Rocks & Minerals 94, n. 3 (11 aprile 2019): 280–85. http://dx.doi.org/10.1080/00357529.2019.1567231.
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Pienaar, D., B. M. Guy, C. Pienaar e K. S. Viljoen. "A geometallurgical characterization study of the Crystalkop Reef at the Great Noligwa Mine, Klerksdorp Goldfield, South Africa". South African Journal of Geology 120, n. 3 (1 settembre 2017): 303–22. http://dx.doi.org/10.25131/gssajg.120.3.303.
Testo completoAbstract (sommario):
Abstract Mineralogical and textural variability of ores from different sources commonly leads to processing inefficiencies, particularly when a processing plant is designed to treat ore from a single source (i.e. ore of a relatively uniform composition). The bulk of the Witwatersrand ore in the Klerksdorp goldfield, processed at the AngloGold Ashanti Great Noligwa treatment plant, is derived from the Vaal Reef (>90%), with a comparatively small contribution obtained from the Crystalkop Reef (or C-Reef). Despite the uneven contribution, it is of critical importance to ensure that the processing parameters are optimized for the treatment of both the Vaal and C-Reefs. This paper serves to document the results of a geometallurgical study of the C-Reef at the Great Noligwa gold mine in the Klerksdorp goldfield of South Africa, with the primary aim of assessing the suitability of the processing parameters that are in use at the Great Noligwa plant. The paper also draws comparisons between the C-Reef and the Vaal Reef A-facies (Vaal Reef) and attempts to explain minor differences in the recovery of gold and uranium from these two sources. Three samples of the C-Reef were collected in-situ from the underground operations at Great Noligwa mine for mineralogical analyses and metallurgical tests. Laboratory-scale leach tests for gold (cyanide) and uranium (sulphuric acid) were carried out using dissolution conditions similar to that in use at the Great Noligwa plant, followed by further diagnostic leaching in the case of gold. The gold in the ore was found to be readily leachable with recoveries ranging from 95% to 97% (as opposed to 89% to 93% for the Vaal Reef). Additional recoveries were achieved in the presence of excess cyanide (96% to 98%). The recovery of uranium varied between 72% and 76% (as opposed to 30% to 64% for the Vaal Reef), which is substantially higher than predicted, given the amount of brannerite in the ore, which is generally regarded as refractory. Thus, the higher uranium recoveries from the C-Reef imply that a proportion of the uranium was recovered by the partial dissolution of brannerite. As the Vaal Reef contain high amounts of chlorite (3% to 8%), which is an important acid consumer, it is considered likely that this could have reduced the effectiveness of the H2SO4 leach in the case of the ore of the Vaal Reef. Since the gold and uranium recoveries from the C-Reef were higher than the recoveries from the Vaal Reef, the results demonstrate that the processing parameters used for treatment of the Vaal Reef are equally suited to the treatment of the C-Reef. Moreover, small processing modifications, such as increased milling and leach retention times, may well increase the recovery of gold (particularly when e.g. coarse gold, or unexposed gold, is present).
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Jones, I. M., e C. R. Anhaeusser. "Accretionary lapilli associated with Archaean banded iron formations of the Kraaipan Group, Amalia greenstone belt, South Africa". Precambrian Research 61, n. 1-2 (febbraio 1993): 117–36. http://dx.doi.org/10.1016/0301-9268(93)90060-f.
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Carney, M. D., e P. J. Mienie. "A geological comparison of the Sishen and Sishen South (Welgevonden) iron ore deposits, Northern Cape Province, South Africa". Applied Earth Science 112, n. 1 (aprile 2003): 81–88. http://dx.doi.org/10.1179/0371745032501171.
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Bau, Michael, e Peter Dulski. "Distribution of yttrium and rare-earth elements in the Penge and Kuruman iron-formations, Transvaal Supergroup, South Africa". Precambrian Research 79, n. 1-2 (luglio 1996): 37–55. http://dx.doi.org/10.1016/0301-9268(95)00087-9.
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28
Hicks, N., e D. J. C. Gold. "A reinterpretation of the Archaean stratigraphy south of Nkandla, southern Kaapvaal Craton, South Africa: Geophysical and stratigraphic constraints on a sheared granitoid-greenstone remnant". South African Journal of Geology 124, n. 3 (1 settembre 2021): 685–98. http://dx.doi.org/10.25131/sajg.124.0025.
Testo completoAbstract (sommario):
Abstract A new lithostratigraphic framework based upon a review of historic data, field mapping and remote sensing, including aerial photography, high-resolution airborne aeromagnetic and radiometric data, is proposed for the Archaean geology along the southeastern margin of the Kaapvaal Craton, South Africa. A synthesis of new and existing data reveals that previously accepted lithostratigraphic schemes require complete revision, with reinterpretations identifying multiple major shear zones and previously unidentified granitoid successions along the margin of the craton. In this new lithostratigraphic framework, lithologies of the Southern Syncline previously correlated with the Nsuze Group of the Pongola Supergroup, are redefined as greenstone lithologies associated with the Ilangwe Greenstone Belt. The geology of the Nkandla region can be subdivided into five distinct geophysical domains including: (i) an extension of the Ilangwe Greenstone Belt, (Domain 1) which is subdivided into; a lower volcanic succession, the Thathe Formation, comprising pillow and amygdaloidal volcanics; the adjoining Sabiza Formation, comprising pillow volcanics exposed in the southeast of the study area; the volcano-sedimentary Mtshwili Formation, which overlies the Thathe and Sabiza formations, consisting of quartz (sericite) schist, phyllite, metavolcanics and iron formation; the Nomangci Formation, which occurs as a region of highly deformed quartz-kyanite-sericite schists, and the Simbagwezi Formation, which comprises maroon to green phyllites and schists in the north of the study area. (ii) granitoids of the Impisi Granitoid Suite (Domain 2) which border the greenstone succession to the north, intruding the Nomangci and Simbagwezi formations. (iii) a southern complex of sheared granitoids termed the Umgabhi Granitoid Suite (Domain 3), which intrudes the Thathe, Sabiza and Mtshwili formations. (iv) The two remaining domains, comprise the Mesoproterozoic Mfongosi and Ntingwe Groups (Domain 4) and Mesoarchaean volcano-sedimentary sequences of the Pongola Supergroup (Domain 5).
29
Reimann, S., C. E. Heubeck, P. Fugmann, D. J. Janse van Rensburg, A. Zametzer, S. H. Serre e T. B. Thomsen. "Syndepositional hydrothermalism selectively preserves records of one of the earliest benthic ecosystems, Moodies Group (3.22 Ga), Barberton Greenstone Belt, South Africa". South African Journal of Geology 124, n. 1 (1 marzo 2021): 253–78. http://dx.doi.org/10.25131/sajg.124.0012.
Testo completoAbstract (sommario):
Abstract The ~3.22 Ga Moodies Group, Barberton Greenstone Belt (BGB), South Africa, provides a unique window into Archaean sedimentary, magmatic and ecological processes. In the central BGB, a regional mafic complex, consisting of a genetically related major mafic sill, a peperitic dyke stockwork, and extensive basaltic lava flows affected thick quartzose sandstones of the Moodies Group. We argue that epithermal hydrothermalism associated with this magmatic event occurred, at least in part, syndepositionally and in places destroyed, in other places preserved the abundant benthic microbial mats in terrestrial- and coastal-facies sandstone of this unit. We differentiate four principal types of hydrothermal alteration: (1) Sericitization resulted from ubiquitous feldspar breakdown; (2) iron-oxide alteration replaced the original matrix by fine-grained iron oxide; (3) silicification replaced matrix and most non-silica grains by microcrystalline silica and locally preserved kerogenous microbial mats; and (4) hydraulic fracturing at shallow depth brecciated consolidated Moodies Group sandstone and created closely spaced, randomly oriented fractures and quartz-filled veins. Because stockwork intrusion locally interacted with unconsolidated water-saturated sediment and because the dykes connect the sill with the mafic lava but also follow zones of structural weakness, we suggest that hydrothermalism associated with this magmatic event occurred syndepositionally but was also – within the resolution of radiometric age data – contemporaneous with tight regional folding. We conclude that microbial organisms in Paleoarchaean coastal (tidal, estuarine) environments may have been formerly widespread, possibly even abundant, but are nearly nowhere preserved because they were easily degradable. Preservation of Early Archaean microbial mats in a thermal aureole in the central BGB was controlled by the “just right” degree of heating and very early hydrothermal silicification.
30
Scoon, R. N., G. Costin e P. J. Gräbe. "Geology and Origin of the Vanadiferous Fe-Ti Oxide-rich Kennedy's Vale Discordant Body, Eastern Limb of the Bushveld Complex, South Africa". South African Journal of Geology 120, n. 2 (1 giugno 2017): 251–70. http://dx.doi.org/10.25131/gssajg.120.2.251.
Testo completoAbstract (sommario):
Abstract The 2055 Ma Bushveld Complex, South Africa, is well known for the occurrence of discordant bodies within the Rustenburg Layered Suite (RLS). Many discordant bodies disrupt mining of layered reefs, but a few have been successfully exploited, including the well known platiniferous dunite pipes. The Kennedy's Vale discordant body, situated in the Steelpoort Valley section of the Eastern Limb, has been almost entirely mined out for a central core of vanadium-rich Ti-magnetite. Discordant bodies are particularly abundant in this area which is severely disrupted by syn-Bushveld doming and faulting. The three-dimensional shape of discordant bodies in the RLS is highly variable, most are pipe-like, but Kennedy's Vale is unusual in that it constitutes an elongate, dyke-like body. The Kennedy's Vale occurrence is emplaced within gabbroic-anorthositic wall rocks of the Lower Main Zone, at a stratigraphic height of several thousands of metres below the Ti-magnetite layers. A broad zonation is recognised and the central core of massive Fe-Ti oxides is enclosed by an inner sheath of iron-rich wehrlite pegmatite and an outer sheath of iron-rich clinopyroxenite pegmatite. The sheath contains disseminated Fe-Ti oxides. An irregular and diffuse reaction rim has been identified between the outer sheath and the wall rocks. Kennedy's Vale is part of the iron-rich ultramafic pegmatite (IRUP) group of discordant bodies, highly unusual rocks characterised by the absence of plagioclase and being more differentiated than the wall rocks in which they are emplaced. The composition of the olivine in the outer sheath at Kennedys' Vale (Fo49.6-46.5) is typical of the IRUP at this stratigraphic height, but considerably more differentiated than the pyroxene in the wall rocks. The reaction rim to the dyke includes relic grains of extremely calcic plagioclase and symplectites, indicative of high-temperature reactions. Symplectites formed due to reaction between the primocrysts in the gabbroic wall rocks and Fe-Ti melts. Kennedy's Vale crystallized from dense, immiscible Fe-Ti oxide-rich melts that drained downward within the RLS into the underlying cumulates with which they reacted. The relatively high vanadium content of the Ti-magnetite in the Kennedy's Vale orebody (average of 2.0 to 2.2 weight % V2O5) is consistent with melts sourced from the lowermost group of Ti-magnetite layers in the Upper Zone. The internal zonation of the dyke is ascribed to contamination of melt with distance from the conduit. The core-zone of massive Fe-Ti oxides was the last component to form as it required a persistent supply of Fe-Ti oxide melt. The absence of core parts of massive Fe-Ti oxides from some bodies of IRUP can be explained by their relatively low stratigraphic height or the relative paucity of introduced melt.
31
Adomako-Ansah, Kofi, Toshio Mizuta, Napoleon Q. Hammond, Daizo Ishiyama, Takeyuki Ogata e Hitoshi Chiba. "Gold Mineralization in Banded Iron Formation in the Amalia Greenstone Belt, South Africa: A Mineralogical and Sulfur Isotope Study". Resource Geology 63, n. 2 (27 marzo 2013): 119–40. http://dx.doi.org/10.1111/rge.12000.
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Mabuza, B. B., e C. W. van Huyssteen. "Effect of synthetic amorphous and crystalline iron oxides on redox potential and exchangeable cations in wetland soils of Maputaland Kwazulu-Natal, South Africa". South African Journal of Geology 119, n. 1 (marzo 2016): 15–24. http://dx.doi.org/10.2113/gssajg.119.1.15.
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Corin, Kirsten, Belinda McFadzean, Natalie Shackleton e Cyril O’Connor. "Challenges Related to the Processing of Fines in the Recovery of Platinum Group Minerals (PGMs)". Minerals 11, n. 5 (18 maggio 2021): 533. http://dx.doi.org/10.3390/min11050533.
Testo completoAbstract (sommario):
In order to increase the recovery of PGMs by flotation, it is necessary to optimise the liberation of the key minerals in which the platinum group elements (PGEs) are contained which include sulphides, arsenides, tellurides, and ferroalloys among others, while at the same time ensuring the optimal depression of gangue minerals. In order to achieve this, comminution circuits usually consist of two or three stages of milling, in which the first stage is autogeneous, followed by ball milling. Further liberation is achieved in subsequent stages using ultra-fine grinding. Each comminution stage is followed by flotation in the so-called MF2 or MF3 circuits. While this staged process increases overall recoveries, overgrinding may occur, hence creating problems associated with fine particle flotation. This paper presents an overview of the mineralogy of most of the more significant PGM ores processed in South Africa and the various technologies used in comminution circuits. The paper then summarises the methodology used in flotation circuits to optimise recovery of fine particles in terms of the collectors, depressants, and frothers used. The effect of entrainment, slimes coating, changes in rheology caused by the presence of a significant amount of fines and of chromite recovery is addressed.
34
Twala, M., R. J. Roberts e C. Munghemezulu. "Detection of magnetite in the Roossenekal area of the Eastern Bushveld Complex, South Africa, using multispectral remote sensing data". South African Journal of Geology 123, n. 4 (16 novembre 2020): 573–86. http://dx.doi.org/10.25131/sajg.123.0041.
Testo completoAbstract (sommario):
Abstract Multispectral sensors, along with common and advanced algorithms, have become efficient tools for routine lithological discrimination and mineral potential mapping. It is with this paradigm in mind that this paper sought to evaluate and discuss the detection and mapping of magnetite on the Eastern Limb of the Bushveld Complex, using high spectral resolution multispectral remote sensing imagery and GIS techniques. Despite the wide distribution of magnetite, its economic importance, and its potential as an indicator of many important geological processes, not many studies had looked at the detection and exploration of magnetite using remote sensing in this region. The Maximum Likelihood and Support Vector Machine classification algorithms were assessed for their respective ability to detect and map magnetite using the PlanetScope Analytic data. A K-fold cross-validation analysis was used to measure the performance of the training as well as the test data. For each classification algorithm, a thematic landcover map was created and an error matrix, depicting the user’s and producer’s accuracies as well as kappa statistics, was derived. A pairwise comparison test of the image classification algorithms was conducted to determine whether the two classification algorithms were significantly different from each other. The Maximum Likelihood Classifier significantly outperformed the Support Vector Machine algorithm, achieving an overall classification accuracy of 84.58% and an overall kappa value of 0.79. Magnetite was accurately discriminated from the other thematic landcover classes with a user’s accuracy of 76.41% and a producer’s accuracy of 88.66%. The overall results of this study illustrated that remote sensing techniques are effective instruments for geological mapping and mineral investigation, especially iron oxide mineralization in the Eastern Limb of the Bushveld Complex.
35
Alchin, D. J., e W. J. Botha. "The structural/stratigraphic development of the Sishen South (Welgevonden) iron ore deposit, South Africa, as deduced from ground gravity data modelling". Applied Earth Science 115, n. 4 (dicembre 2006): 174–86. http://dx.doi.org/10.1179/174327506x138940.
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36
Hicks, N., D. J. C. Gold, M. Ncume e L. Hoyer. "A new lithostratigraphic framework for portions of the Pongola Supergroup within the Nkandla sub-basin, southern Kaapvaal Craton, South Africa; insights into Mozaan Group stratigraphy". South African Journal of Geology 124, n. 3 (1 settembre 2021): 717–34. http://dx.doi.org/10.25131/sajg.124.0039.
Testo completoAbstract (sommario):
Abstract A revised lithostratigraphic framework for Mozaan Group-equivalent strata within the Nkandla sub-basin is presented based on new field data, remote sensing and genetic sequence stratigraphic interpretations. Although previous literature has suggested that no Mozaan Group lithologies were deposited within the sub-basin, reinterpretations presented here indicate that 90% of the lithostratigraphy developed within the main basin occurs within the Nkandla and Mhlatuze inliers. Mozaan Group units previously defined as the Vutshini and Ekombe formations are correlated with stratigraphy from the lowermost Sinqeni Formation to the Gabela Formation. Although thinner than units within the type area in the main basin, thicknesses of the Sinqeni Formation are comparable to those observed within the White Mfolozi Inlier. A ~1 000 m composite reference profile is measured within the Mdlelanga Syncline of the Nkandla Inlier. Further profiles were measured for sequences in the Gem-Vuleka Syncline of the Nkandla Inlier, as well as within the Mhlatuze Inlier. These latter profiles, however, host only lower Mozaan Group strata. In all sections the basal portion of the sequence comprises two quartz arenite units, separated by a ferruginous shale, which hosts minor iron formation interbeds. This predominantly coarse-grained lower sequence is overlain by a shale-dominated succession with multiple sandstone interbeds. A prominent coarse-grained quartz arenite unit forms a distinct marker in the middle portion of the sequence. This is overlain by a sequence of shales and sandstones with two prominent igneous units present. Genetic sequence stratigraphic interpretations indicate cyclical deposition of dominantly shallow marine sediments with condensed sections, marked by iron formations or ferruginous shales, denoting periods of marine highstand along the southeastern margin of the Kaapvaal Craton. The evidence of Mozaan Group stratigraphy within the Nkandla sub-basin supports a passive margin tectonic model whereby deposition occurred in an arcuate shallow continental margin which opened to the southeast. The extension of Mozaan Group strata into the Nkandla sub-basin suggests that the Mozaan Basin likely formed a single depository rather than separate sub-basins as previously proposed.
37
Boneschans, R. B., M. S. Coetzee e S. J. Siebert. "A geobotanical investigation of the Koedoesfontein Complex, Vredefort Dome, South Africa". Australian Journal of Botany 63, n. 4 (2015): 324. http://dx.doi.org/10.1071/bt14267.
Testo completoAbstract (sommario):
The Vredefort Dome (impact structure) in South-Africa hosts several unique peralkaline to ultramafic intrusive bodies that were emplaced into its core and collar. Because of the broad difference in mineral composition, between the intrusions as well as the abundant siliciclastic country rocks, abrupt transitions in soil chemical characteristics are produced that can ultimately affect the floristic and physiognomic characteristics of the associated vegetation in the dome. Despite various efforts to study the ultramafic-adapted vegetation of southern Africa, little is known about the effect these particular intrusions have on the soil and floristical components of the dome. The aim of the present study was to investigate the geobotany of one of the ultramafic-peralkaline complexes in the dome, namely the Koedoesfontein Complex. The complex hosts several different intrusions that collectively form a mineralogical gradient ranging from mafic- to felsic-dominant silicates. Three primary components (geology, soil and woody vegetation) were sampled along this gradient and analysed to determine the effect of these intrusions on the residual soil chemistry, and the floristics and physiognomy of the supported vegetation type. Weathering of the peralkaline to ultramafic lithologies greatly affected the soil’s chemical properties and related species composition and physiognomy. Major chemical variation in the soil, including the total chromium and nickel content, is correlated with the difference in abundance of sodium-, calcium-, iron- and magnesium-rich silicate minerals. Significant variations in woody species composition (particularly across Senegalia and Vachellia genera) have been established between soils originating from ultramafic–mafic, intermediate and felsic rock types and can be utilised as indicators for different geological substrates within the dome.
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Tsikos, H., J. M. Moore e C. Harris. "Geochemistry of the Palæoproterozoic Mooidraai Formation: Fe-rich limestone as end member of iron formation deposition, Kalahari Manganese Field, Transvaal Supergroup, South Africa". Journal of African Earth Sciences 32, n. 1 (gennaio 2001): 19–27. http://dx.doi.org/10.1016/s0899-5362(01)90016-8.
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Dayet, Laure. "Invasive and Non-Invasive Analyses of Ochre and Iron-Based Pigment Raw Materials: A Methodological Perspective". Minerals 11, n. 2 (17 febbraio 2021): 210. http://dx.doi.org/10.3390/min11020210.
Testo completoAbstract (sommario):
Naturally occurring and deeply coloured iron-bearing materials were exploited very early on by human populations. The characterization of these materials has proven useful for addressing several archaeological issues, such as the study of technical behaviors, group mobility, and the reconstruction of cultural dynamics. However, this work poses some critical methodological questions. In this paper, we will review ochre studies by focusing on the analytical methods employed, the limits of non-invasive methods, as well as examples of some quality research addressing specific issues (raw material selection and provenience, heat treatment). We will then present a methodological approach that aims to identify the instrumental limits and the post-depositional alterations that significantly impact the results of the non-invasive analysis of cohesive ochre fragments from Diepkloof rock Shelter, South Africa. We used ochre materials recuperated in both archaeological and geological contexts, and we compared non-invasive surface analyses by XRD, scanning electron microscopy coupled with dispersive X-ray spectrometry (SEM-EDXS), and particle-induced X-ray emission (PIXE) with invasive analysis of powder pellets and sections from the same samples. We conclude that non-invasive SEM-EDXS and PIXE analyses provide non-representative results when the number of measurements is too low and that post-depositional alterations cause significant changes in the mineralogical and major element composition at the surface of archaeological pieces. Such biases, now identified, must be taken into account in future studies in order to propose a rigorous framework for developing archaeological inferences.
40
Polomé, L. G. B. T. "The application of the mise-a-la-masse electrical technique in Greenstone belt gold exploration". Exploration Geophysics 20, n. 2 (1989): 113. http://dx.doi.org/10.1071/eg989113.
Testo completoAbstract (sommario):
Most of the gold deposits in the Barberton Greenstone belt of South Africa are relatively small and in structurally complex geological areas.The mise-a-la-masse electrical technique, where a current electrode is earthed in a mineralised zone, was used on one of our exploration projects consisting of a sulphides/gold-bearing carbonaceous banded iron formation within a succession of mafic, ultramafic and sedimentary rocks. The technique was successful in delineating individual mineralised units within a broad lithological sequence. During the survey, electrical potential measurements were recorded on surface, in underground drives and in twenty five boreholes. Measurements were also repeated by earthing the mineralised zone in a number of boreholes. Major discontinuities were recognised within the ore zones and used to interpret geological structures. These were then used to define specific units for ore reserve calculations and the application of selected mining techniques.
41
Varentsov, I. M., e V. N. Kuleshov. "Rare Elements—Markers of the Formation Setting of Manganese and Iron Ore Deposits in the Kalahari and Postmasburg Fields (South Africa): Communication 1. Kalahari Manganese Field". Lithology and Mineral Resources 54, n. 4 (28 giugno 2019): 333–49. http://dx.doi.org/10.1134/s0024490219040060.
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Selmi, Moustafa, Leonardo E. Lagoeiro e Issamu Endo. "Geochemistry of hematitite and itabirite, Quadrilátero Ferrífero, Brazil". Rem: Revista Escola de Minas 62, n. 1 (marzo 2009): 35–43. http://dx.doi.org/10.1590/s0370-44672009000100006.
Testo completoAbstract (sommario):
Twenty-one samples of hematitite and twelve samples of itabirite were collected from different deposits of the Quadrilátero Ferrífero (QF) area and were analyzed for trace and rare earth elements. The purpose of the study is to understand the element distribution in the QF in comparison with other iron formations (IF) around the world. Trace element contents are relatively low with considerable variability, being lower than the contents in the Algoma IF, Anamikie IF, Maru IF in Nigeria and Orissa IF in India. REE's abundance is relatively low, but higher than REE's of Hamersley IF of Western Australia, Surgur belt in India and lower than Kuruman IF in South Africa. Chondrite normalized patterns show slight degrees of fractionation for LREE to HREE and slightly positive Eu anomalies coupled with positive values of (La/Yb)CN and (La/Sm)CN ratios.
43
Johnson, J. E., S. M. Webb, C. B. Condit, N. J. Beukes e W. W. Fischer. "Effects of metamorphism and metasomatism on manganese mineralogy: Examples from the Transvaal Supergroup". South African Journal of Geology 122, n. 4 (1 dicembre 2019): 489–504. http://dx.doi.org/10.25131/sajg.122.0034.
Testo completoAbstract (sommario):
AbstractManganese-bearing minerals in ancient strata provide a particularly informative record of the redox potentials of ancient Earth surface environments due to the high specificity of species that can oxidize Mn(II). However, little is known about how this sedimentary archive might have been altered by processes occurring long after lithification, including the effects of metamorphism, fluid mobilization, and metasomatism. We investigated Mn mineralization across known metamorphic gradients in the Kaapvaal craton, South Africa, in Archean and early Paleoproterozoic age carbonate-, shale-, and iron formation-bearing marine strata. We sampled contemporaneous strata that record the drowning of the Campbellrand-Malmani carbonate platform and a transition to iron formation deposition in a range of localities, from two metamorphosed (greenschist and above, affected by the intrusion of the Bushveld igneous complex) and four better-preserved (sub-greenschist) deep subsurface drill cores. To evaluate the geochemistry and mineralization tied directly to petrographic textures and cross-cutting relationships, we combined bulk geochemistry with light and electron microscopy and synchrotron microprobe X-ray absorption spectroscopy and imaging to produce Mn speciation maps at the requisite micrometer length scales for these textures. Samples with lesser degrees of post-depositional transformation contained minor amounts of Mn(II) in early diagenetic marine carbonate cements and detrital carbonate grains, while metamorphosed samples typically contained Mn concentrated into a combination of coarse-grained and vein-filling carbonate phases (ankerite, siderite, and rhodochrosite), garnet and amphibole. Chemical imaging analyses of these more metamorphosed samples show that Mn is held by phases and textures that mineralized post-deposition and lithification, demonstrating that Mn was mobilized – at least locally – by metasomatic fluids, although it is difficult to distinguish whether this Mn was original to these strata or was introduced secondarily. Our results confirm that Mn can be mobilized and therefore caution should be applied when interpreting Mn enrichments in sedimentary rocks, especially when Mn enrichment is not geographically extensive and coincides with metamorphic processes.
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Mameshin, V., e S. Zhuravlova. "Modern condition and development prospects of alternative processes of the ferrous metallurgy". Theory and practice of metallurgy, n. 6 (20 novembre 2018): 71–75. http://dx.doi.org/10.34185/tpm.6.2018.09.
Testo completoAbstract (sommario):
Nowadays a significant number of alternative processes of ferrous metals production have been developed, it differs in the principles of operation, as well as the design arrangement of the aggregates. In general, "alternative" processes of ferrous metals production can be divided into 4 groups. The processes of the first group (the production of sponge iron in direct reduction units with remelting in electric arc furnaces) are based on the use of reduction gases (CO, H2 or a mixture of them) or coal for the reduction. Depending on this, they have different principles of work and design. Shaft processes of direct reduction, based on the use of reduction gases, have the dominant positions in the global production of HBI. This is due to the design simplicity of these units, the reliability of their work and the low content of harmful impurities (S, P) in the products. The principle of the processes of the second group (production of carbon semi-products in smelting reduction units with blowing in BOF) involves the reduction of iron ore with power-generating coal at temperatures of 1400-1600 °C and obtaining hot metal. The processes of this group can use as a charge partially reduced iron ore materials (Corex processes, Finex, Tecnored, etc.), as well as raw iron ore (processes Hismelt, Romelt, Ausiron). More than forty processes in various countries have been developed and tested to substitute blast furnace process. Currently, there are 7 Corex units in the world (2 - China, 4 - India, 1 - South Africa) with a total annual productivity of about 7 million tons; 3 Finex units (2 in Korea, 1 in India) with an annual productivity of about 3.5 million tons. The development of processes for the direct production of steel from iron ore (the third group) is currently focused on the processing of iron-containing waste (sludge, scale, dust iron ore) to crude steel. Examples include: the process of jet-emulsion refining, production of high carbon steel in rotary inclined furnaces or perspective direct electrolysis processes of iron ore (MOE), the development of which is at the initial stages of laboratory research. Continuous processes for the production of crude steel from hot metal (the fourth group), due to difficulties in controlling a continuous process, high consumption of refractories, low economic indexes and, most importantly, the rapid growth of ladle treatment of steel, could not compete with the LD-process and are currently hardly used. It should be said about the prospects of the considered alternative processes for the ferrous metals production. The processes of direct reduction have proven their competitiveness, the prospects of their development is determined by the need of electric steelmaking in high-quality metal charge. At the moment smelting reduction processes of ferrous metals production are not the real competitors to BF process and so far they should be considered only as an addition to it. However, if the price of metallurgical coke continues to grow, then the further spread of smelting reduction processes is possible. The processes of the third group are directed to the utilization of iron-containing metallurgical wastes and dust iron ores, but the development of majority of these processes is on its initial stages, their prospects will be determined by economic efficiency. Continuous steelmaking processes with use of hot metal as a charge could not clearly prove their superiority to the well-known steelmaking processes, at this stage their prospects are rather doubtful.
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Pirajno, Franco. "Mineral systems and their putative link with mantle plumes". Geological Society, London, Special Publications, 5 maggio 2021, SP518–2020–276. http://dx.doi.org/10.1144/sp518-2020-276.
Testo completoAbstract (sommario):
AbstractIn this contribution, I discuss the putative link of mantle plumes with selected categories of mineral systems. Continental rifting and break-ups can be induced by the upwelling of mantle plumes, also resulting in the generation of a wide range of mineral deposits. These include magma-associated ores, anorogenic igneous events responsible for iron oxide–copper–gold (IOCG) deposits, carbonatites and hydrothermal-induced mineralization, as well as hydrocarbons, salt domes, petroleum and gas, and several mineral systems in continental passive margins. Amongst the magma-associated mineral systems, the Ni–Cu–platinum group element (PGE), Fe–Ti–V and Cr deposits are the economically most important, such as those of the Bushveld Igneous Complex in South Africa. Anorogenic magmas are generally alkaline and associated with IOCG mineral systems, as exemplified by the giant Olympic Dam and similar deposits in South America. Carbonatites are considered as a distal effect of hotspot mantle plumes, as shown by Mount Weld in Australia, which may be related to the Bushveld Superplume. Plume-related thermal anomalies are the principal factor for the inception of hydrothermal circulation and the genesis of a wide range of hydrothermal mineral systems in rift-related tectonic settings. These include large-scale sedimentary-rock-hosted metalliferous ores, such as sedimentary exhalative (SEDEX) deposits. A modern example of is provided by the Red Sea brine pools. Some key examples are presented in this paper.
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Vearncombe, J. R., N. J. McNaughton, J. K. Porter, J.-W. Zi e C. Talavera. "Age of the Archaean Murchison Belt and mineralisation, South Africa". South African Journal of Geology, 9 novembre 2020. http://dx.doi.org/10.25131/sajg.124.0001.
Testo completoAbstract (sommario):
Abstract The east-northeast-trending Murchison-Thabazimbi Lineament in northern South Africa is one of the world’s most important structures for its control on world-class mineral deposits, Proterozoic sedimentary basins and giant igneous intrusions. The deepest exposed Archaean parts of the lineament are the Murchison Belt. Bounded by granitoids, the belt comprises greenschist to amphibolite facies volcano-sedimentary strata with isoclinal folds and the 7 km thick meta-igneous Rooiwater Complex. The Rooiwater Complex is intruded by a northern regional granitoid dated at 2 929 ± 7 Ma by SHRIMP U-Pb on zircons. Using field relationships, published isotopic age data and new SHRIMP zircon dates we confirm the age Rooiwater Complex at 2 965 Ma, showing it to be contemporaneous with the Archaean volcanic and sedimentary formations, the meta-igneous Complex being the lower sequence in a ~2 980 to 2 960 Ma island arc. Despite being implicated as a source of gold for the world’s largest natural accumulation of gold in the Witwatersrand Basin, the absolute age of Sb-Au mineralisation in the Murchison Belt is poorly constrained. We have utilised SHRIMP U-Pb geochronology to date monazites from a Sb-Au ore sample from the granitoid-hosted Malati Pump orebody and determine ages for two different generations of monazite, both associated with ore minerals. The older age of 2 832 ± 23 Ma is from a minority of grains and is interpreted to date the primary Sb-Au mineralisation, about 120 Ma after belt formation. This age predates, or is possibly synchronous with, sedimentation of the upper-Witwatersrand Central Rand Group. The younger age of 1 968 ± 17 Ma from a majority of monazite grains is unrelated in time to known events and interpreted here as a cryptic hydrothermal reworking of the Sb-Au ores in this deposit.
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Avery, D. M. "Micromammals and the Late Quaternary of southern Africa". South African Journal of Geology, 31 luglio 2021. http://dx.doi.org/10.25131/sajg.124.0035.
Testo completoAbstract (sommario):
Abstract Improvements in excavation methods, dating, analytical techniques and statistical applications have all led to a substantial increase in recoverable environmental evidence from micromammals. Because these animals are so small the information they provide is on a smaller geographical scale than that afforded by most other lines of evidence. However, with increasing amounts of data and greater interpretational precision in all spheres, the chances are improving of being able to mesh information from different scales. Blombos, Pinnacle Point and Klasies River on the southern coast of South Africa have clearly demonstrated that micromammalian data can contribute to multidisciplinary interpretations of past conditions, in this case during MIS 5 and 6. Little attention has been paid to the generally small samples from Iron Age sites but the presence of the House rat Rattus rattus may provide important information about human movements and may also contribute to our understanding of the Anthropocene once this has been formally defined. Micromammals have not yet been used as chronostratigraphic indicators in southern Africa but it may be possible to develop biochronologies using them and to incorporate this material into African Land Mammal Ages.
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Moloko, K. G., e J. W. van der Merwe. "Investigation of the mechanism for fireside corrosion in coal-fired boilers in South Africa". Journal of the Southern African Institute of Mining and Metallurgy 121, n. 6 (2021). http://dx.doi.org/10.17159/2411-9717/951/2021.
Testo completoAbstract (sommario):
SYNOPSIS Furnace wall tubes from 600 MW subcritical boilers at three coal-fired power stations were sampled and the fireside deposits examined to determine the mechanism of fireside corrosion. This involved an in-depth investigation into the morphology and composition of the fireside deposits and the conditions of the furnace that enable this type of attack. SEM-EDS analysis revealed high concentrations of oxygen, iron, and sulphur, QEMSCAN and XRD analyses identified the presence of Fe3O4, Fe2O3, FeS, and FeS2. Differential thermal analysis showed thermal activities at temperatures of 500-600°C, 900-1100°C, and 1100-1250°C, which are associated, respectively, with FeS2 oxidation to FeS and Fe2O3, at 475-525°C, formation of aluminosilicates at 925-1100°C, and melting of FeS around 1190°C. The absence of sodium and potassium eliminates the contribution of molten alkali sulphates to the corrosion. The consistent coexistence of iron sulphide and iron oxide is indicative of the substoichiometric conditions in the furnace, while the detection of pyrite suggests that the coal is not completely combusted, which points to a poor combustion process. These observations were affirmed by gas analysis at one of the stations, where very high levels of carbon monoxide were measured at the furnace wall (> 14 000 ppm) and furnace exit (> 3500 ppm). The high CO concentrations are indicative of limited combustion caused by limited O2. These reducing conditions promote the formation of FeS-rich deposit, which is the corrosive species responsible for degradation. Keywords: fireside corrosion, sulphidation, coal-fired boiler, furnace wall tubes.
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Rasmussen, Birger, Janet R. Muhling, Alexandra Suvorova e Woodward W. Fischer. "Apatite nanoparticles in 3.46–2.46 Ga iron formations: Evidence for phosphorus-rich hydrothermal plumes on early Earth". Geology, 5 febbraio 2021. http://dx.doi.org/10.1130/g48374.1.
Testo completoAbstract (sommario):
Phosphorus is an essential nutrient that is thought to have regulated primary productivity in global oceans after the advent of oxygenic photosynthesis. The prime source of seawater phosphorus is regarded to be continental weathering of phosphate minerals. Ancient seawater phosphorus concentrations have been constrained using the phosphorus content of iron-rich chemical sediments—banded iron formations (BIFs); however, the removal processes and depositional phases remain unclear. Here we report that nanometer-sized apatite crystals (<500 nm) are ubiquitous in 3.46–2.46 Ga BIFs and cherts from the Kaapvaal (South Africa) and Yilgarn and Pilbara (Western Australia) cratons. The apatite is uniformly dispersed in a chemical sediment comprising greenalite nanoparticles, which were encased in very early diagenetic silica cement that limited compaction and chemical reactions. The lack of organic carbon (below detection; <0.3 wt%) and absence of primary iron oxides implies that the phosphorus was not derived from the degradation of organic matter or seawater scavenging by oxide particles. Instead, the occurrence of apatite in sediments derived from hydrothermally sourced Fe2+ and SiO2(aq) suggests that phosphorus too was derived from vent plumes. Today, seawater P is rapidly removed from vent fluids due to scavenging by oxidized Fe2+. However, prior to the Great Oxidation Event (2.45–2.32 Ga), dissolved phosphorus released during anoxic alteration of seafloor basalts escaped the iron-oxidation trap. Our results point to the existence of a submarine hydrothermal flux of dissolved phosphorus that supplied nutrients to the early anoxic oceans. High amounts of seawater P may help to explain why phosphorus is ubiquitous in cell biology—it was not limiting during the origin and early evolution of life.
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Pollock, Zach, e Camille Partin. "Geobiology of the Paleoproterozoic Belcher Group, Nunavut, Canada". USURJ: University of Saskatchewan Undergraduate Research Journal 6, n. 1 (5 marzo 2020). http://dx.doi.org/10.32396/usurj.v6i1.507.
Testo completoAbstract (sommario):
The ~2.0-1.8 Ga (billion years old) Belcher Group on the Belcher Islands in Nunavut provide a unique opportunity for studying Paleoproterozoic geobiology. The Belcher Group includes a sequence of low metamorphic grade peritidal carbonate rocks that preserve putative microbiota, as first described by Hofmann and Jackson (1969). Microbial mats, including stromatolites, are abundant in the peritidal carbonate succession. Additionally, morphologies possibly related to blue-green algae were first described in granular iron formation rocks of the Belcher Group by Moore (1918). The Belcher Group microbiota are a group of simple organisms, believed to be prokaryotic in nature. Microbiota morphologies include ellipsoids, spheroids, and filamentous chains of cells interpreted by previous workers to represent blue-green algae and acritarchs. Some microstructures are questionably biogenic and might be abiotic. The most significant field studies on the Belcher Group occurred from the late 1950s to the early 1980s, which provides the geological context for this study. This project aims to build on the previous work of H. Hofmann and others in the ‘60s and bring these microbiota into a modern context, drawing on the analytical advancements of the last 50 years. The main goal of the project is to determine if there is evidence that the microbiota are perhaps eukaryotic organisms. The emergence of eukaryotes is arguably the most significant geobiological event in Earth history, with eukaryotic cells believed to have evolved around 1.6 Ga (Knoll et al. 2006; Javaux and Lepot 2018), but some contentious fossils interpreted to represent eukaryotes have been dated to as early as 2.2 Ga (Retallack et al. 2013). In North America, the oldest discovered eukaryotic remains are around 1.5 Ga (Adam et al. 2017). If eukaryotic fossils were to be discovered in the Belcher Group, this would make them the oldest occurrence in North America. To test the hypothesis, samples from the microbiota-containing units were collected on the Belcher Islands. Both light microscopy and a collection of modern analytical techniques will be used to obtain high resolution images and chemical signatures of the microbiota and their biosignatures. Preliminary data from petrography, Raman Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS) will be presented. Both Raman spectroscopy and XPS have been used as characterization tools in other studies looking at microbiota and organic matter remains (Qu et al. 2018; Arnarson and Keil 2001). Raman collects molecular and structural data from the sample, while XPS collects elemental chemical data. Both techniques are therefore particularly useful for identifying and characterizing organic carbon, which is the base of organic matter.
References:
Adam, Zachary R., Mark L. Skidmore, David W. Mogk, and Nicholas J. Butterfield. 2017. “A Laurentian Record of the Earliest Fossil Eukaryotes.” Geology 45 (5): 387–90. https://doi.org/10.1130/G38749.1.
Arnarson, Thorarinn S., and Richard G. Keil. 2001. “Organic–Mineral Interactions in Marine Sediments Studied Using Density Fractionation and X-Ray Photoelectron Spectroscopy.” Organic Geochemistry 32 (12): 1401–15. https://doi.org/10.1016/S0146-6380(01)00114-0.
Hofmann, H. J., and G. D. Jackson. 1969. “Precambrian (Aphebian) Microfossils from Belcher Islands, Hudson Bay.” Canadian Journal of Earth Sciences 6 (5): 1137–44. https://doi.org/10.1139/e69-115.
Javaux, Emmanuelle J., and Kevin Lepot. 2018. “The Paleoproterozoic Fossil Record: Implications for the Evolution of the Biosphere during Earth’s Middle-Age.” Earth-Science Reviews 176 (January): 68–86. https://doi.org/10.1016/j.earscirev.2017.10.001.
Knoll, A.H, E.J Javaux, D Hewitt, and P Cohen. 2006. “Eukaryotic Organisms in Proterozoic Oceans.” Philosophical Transactions of the Royal Society B: Biological Sciences 361 (1470): 1023–38. https://doi.org/10.1098/rstb.2006.1843.
Moore, E. S. 1918. “The Iron-Formation on Belcher Islands, Hudson Bay, with Special Reference to Its Origin and Its Associated Algal Limestones.” The Journal of Geology 26 (5): 412–38.
Qu, Yuangao, Shixing Zhu, Martin Whitehouse, Anders Engdahl, and Nicola McLoughlin. 2018. “Carbonaceous Biosignatures of the Earliest Putative Macroscopic Multicellular Eukaryotes from 1630 Ma Tuanshanzi Formation, North China.” Precambrian Research 304 (January): 99–109. https://doi.org/10.1016/j.precamres.2017.11.004.
Retallack, Gregory J., Evelyn S. Krull, Glenn D. Thackray, and Dula Parkinson. 2013. “Problematic Urn-Shaped Fossils from a Paleoproterozoic (2.2Ga) Paleosol in South Africa.” Precambrian Research 235 (September): 71–87. https://doi.org/10.1016/j.precamres.2013.05.015.