Modern gold deportment studies include physical, chemical and mineralogical assessments, combined... more Modern gold deportment studies include physical, chemical and mineralogical assessments, combined to obtain a full understanding of the nature and variability of gold in a resource. The objective is to provide information which will allow cost effective and practical processing by informing decisions regarding resource evaluation, mining method and extraction process optimization. The distribution of gold, based on speciation, grain size and mode of occurrence (liberation, exposure, and mineral association) is quantitatively determined by means of automated Scanning Electron Microscopic Techniques (QEMSCAN/MLA). Furthermore, general mineralogical characterization is undertaken in order to characterize the gangue components; with special emphasis on deleterious characteristics of the ore (e.g. cyanide consumers such as secondary Cu-species, preg-robbers/borrowers, passivation due to Sb-minerals or As-minerals and oxygen consumers such as pyrrhotite/marcasite). Predictions based on the mineralogical observations are confirmed by physical and chemical testwork. These include grading analyses, gravity separation, direct cyanidation, and diagnostic (sequential) leach tests.
Abstract Due to the variability and complex nature of REE-containing ores, it is vital to underst... more Abstract Due to the variability and complex nature of REE-containing ores, it is vital to understand the mineralogical characteristics, before embarking on any metallurgical testwork campaign. REE’s are present in a variety of phases/minerals, all of which may react differently during processing. It is therefore important to identify and quantify all the REE-phases present in the ore, their mineral associations, grain size distributions as well as their liberation characteristics. In order to quantify the elemental deportment of the different REE’s into the different REE-bearing phases, it is necessary to determine the mineral chemical compositions by Electron Microprobe. By assigning the average measured REE-elemental compositions to the different REE-phases, it becomes possible to determine the amount of each REE per REE-phase. Predictions about the best theoretically achievable grades and recoveries can be made. The data obtained are used to design a metallurgical testwork program suitable for the specific ore-type.
Modern gold deportment studies include physical, chemical and mineralogical assessments, combined... more Modern gold deportment studies include physical, chemical and mineralogical assessments, combined to obtain a full understanding of the nature and variability of gold in a resource. The objective is to provide information which will allow cost effective and practical processing by informing decisions regarding resource evaluation, mining method and extraction process optimization. The distribution of gold, based on speciation, grain size and mode of occurrence (liberation, exposure, and mineral association) is quantitatively determined by means of automated Scanning Electron Microscopic Techniques (QEMSCAN/MLA). Furthermore, general mineralogical characterization is undertaken in order to characterize the gangue components; with special emphasis on deleterious characteristics of the ore (e.g. cyanide consumers such as secondary Cu-species, preg-robbers/borrowers, passivation due to Sb-minerals or As-minerals and oxygen consumers such as pyrrhotite/marcasite). Predictions based on the mineralogical observations are confirmed by physical and chemical testwork. These include grading analyses, gravity separation, direct cyanidation, and diagnostic (sequential) leach tests.
levels (that is, greater than 10 25 times that of the present atmospheric level) during the depos... more levels (that is, greater than 10 25 times that of the present atmospheric level) during the deposition of these units. The presence of rounded pebbles of sideritic iron formation at the base of the Rooihoogte Formation and an extensive and thick ironstone layer consisting of haematitic pisolites and oolites in the upper Timeball Hill Formation indicate that atmospheric oxygen rose
The Paleoproterozoic Duitschland Formation lies stratigraphically beneath the Timeball Hill Forma... more The Paleoproterozoic Duitschland Formation lies stratigraphically beneath the Timeball Hill Formation, which contains the only unequivocal glacial unit of this era in the Transvaal Basin, South Africa. Lithologic evidence in Paleoproterozoic successions of North America, however, indicates the existence of three discrete and potentially global ice ages within this 300 my interval. Carbonates of the Duitschland Formation are significantly enriched in 13 C up to ؉10.1 permil in the upper part of the succession above a notable sequence boundary. In contrast, the lower part of this unit contains carbonates with consistently negative ␦ 13 C values. Trace and major element compositions of these carbonates as well as carbon-isotopic compositions of coexisting organic matter support a primary origin for the markedly positive carbon isotope anomaly. The stratigraphic constraints indicate that 13 C-enriched carbonates were deposited prior to Paleoproterozoic glaciation in southern Africa, similar to carbonates stratigraphically beneath Neoproterozoic glacial diamictites worldwide. Also mirroring the Neoproterozoic record are strongly negative ␦ 13 C values in cap carbonates atop glacial diamictites in Paleoproterozoic strata of Wyoming and Ontario. The litho-and chemostratigraphic constraints indicate that the interval of negative carbon isotope values in well-preserved carbonates of the lower Duitschland Formation may reflect a second Paleoproterozoic ice age in the Transvaal succession. This interpretation is further supported by recently discovered bullet-shaped clasts with striations in diamictite from the basal part of the succession. Thus, the emerging temporal pattern of carbon isotope variations and glaciation in the Paleoproterozoic has a close analogue to Neoproterozoic events, suggesting a coupling of climatic and biogeochemical changes at both ends of the eon. introduction The Paleoproterozoic Era (1.6-2.5 Ga) is a distinct interval in Earth history characterized by interrelated tectonic, evolutionary, climatic, and biogeochemical events resulting in broad changes of Earth's surface environments. The detailed relationship between key transitions is poorly understood, however, due to uncertainties in correlation and the age of sedimentary successions where critical events are preserved, as well as stratigraphic omissions and post-depositional insults that obscure the true nature of temporal trends. For example, in North America, three discrete levels of Paleoproterozoic glacial diamictites are recognized in the Huronian and Snowy Pass supergroups of Ontario and Wyoming (Young, 1973, 1988; Ojakangas, 1985), respectively; on other continents only a single unequivocal diamictite of glacial origin has thus far been recognized (Ojakangas, 1985). In North America, these ice ages are radiometrically constrained to have occurred over a 230 my interval between 2.22 and 2.45 Ga (fig. 1; Krogh, Davis, and Corfu, 1984; Corfu and Andrews, 1986).
Modern gold deportment studies include physical, chemical and mineralogical assessments, combined... more Modern gold deportment studies include physical, chemical and mineralogical assessments, combined to obtain a full understanding of the nature and variability of gold in a resource. The objective is to provide information which will allow cost effective and practical processing by informing decisions regarding resource evaluation, mining method and extraction process optimization. The distribution of gold, based on speciation, grain size and mode of occurrence (liberation, exposure, and mineral association) is quantitatively determined by means of automated Scanning Electron Microscopic Techniques (QEMSCAN/MLA). Furthermore, general mineralogical characterization is undertaken in order to characterize the gangue components; with special emphasis on deleterious characteristics of the ore (e.g. cyanide consumers such as secondary Cu-species, preg-robbers/borrowers, passivation due to Sb-minerals or As-minerals and oxygen consumers such as pyrrhotite/marcasite). Predictions based on the mineralogical observations are confirmed by physical and chemical testwork. These include grading analyses, gravity separation, direct cyanidation, and diagnostic (sequential) leach tests.
Abstract Due to the variability and complex nature of REE-containing ores, it is vital to underst... more Abstract Due to the variability and complex nature of REE-containing ores, it is vital to understand the mineralogical characteristics, before embarking on any metallurgical testwork campaign. REE’s are present in a variety of phases/minerals, all of which may react differently during processing. It is therefore important to identify and quantify all the REE-phases present in the ore, their mineral associations, grain size distributions as well as their liberation characteristics. In order to quantify the elemental deportment of the different REE’s into the different REE-bearing phases, it is necessary to determine the mineral chemical compositions by Electron Microprobe. By assigning the average measured REE-elemental compositions to the different REE-phases, it becomes possible to determine the amount of each REE per REE-phase. Predictions about the best theoretically achievable grades and recoveries can be made. The data obtained are used to design a metallurgical testwork program suitable for the specific ore-type.
Modern gold deportment studies include physical, chemical and mineralogical assessments, combined... more Modern gold deportment studies include physical, chemical and mineralogical assessments, combined to obtain a full understanding of the nature and variability of gold in a resource. The objective is to provide information which will allow cost effective and practical processing by informing decisions regarding resource evaluation, mining method and extraction process optimization. The distribution of gold, based on speciation, grain size and mode of occurrence (liberation, exposure, and mineral association) is quantitatively determined by means of automated Scanning Electron Microscopic Techniques (QEMSCAN/MLA). Furthermore, general mineralogical characterization is undertaken in order to characterize the gangue components; with special emphasis on deleterious characteristics of the ore (e.g. cyanide consumers such as secondary Cu-species, preg-robbers/borrowers, passivation due to Sb-minerals or As-minerals and oxygen consumers such as pyrrhotite/marcasite). Predictions based on the mineralogical observations are confirmed by physical and chemical testwork. These include grading analyses, gravity separation, direct cyanidation, and diagnostic (sequential) leach tests.
levels (that is, greater than 10 25 times that of the present atmospheric level) during the depos... more levels (that is, greater than 10 25 times that of the present atmospheric level) during the deposition of these units. The presence of rounded pebbles of sideritic iron formation at the base of the Rooihoogte Formation and an extensive and thick ironstone layer consisting of haematitic pisolites and oolites in the upper Timeball Hill Formation indicate that atmospheric oxygen rose
The Paleoproterozoic Duitschland Formation lies stratigraphically beneath the Timeball Hill Forma... more The Paleoproterozoic Duitschland Formation lies stratigraphically beneath the Timeball Hill Formation, which contains the only unequivocal glacial unit of this era in the Transvaal Basin, South Africa. Lithologic evidence in Paleoproterozoic successions of North America, however, indicates the existence of three discrete and potentially global ice ages within this 300 my interval. Carbonates of the Duitschland Formation are significantly enriched in 13 C up to ؉10.1 permil in the upper part of the succession above a notable sequence boundary. In contrast, the lower part of this unit contains carbonates with consistently negative ␦ 13 C values. Trace and major element compositions of these carbonates as well as carbon-isotopic compositions of coexisting organic matter support a primary origin for the markedly positive carbon isotope anomaly. The stratigraphic constraints indicate that 13 C-enriched carbonates were deposited prior to Paleoproterozoic glaciation in southern Africa, similar to carbonates stratigraphically beneath Neoproterozoic glacial diamictites worldwide. Also mirroring the Neoproterozoic record are strongly negative ␦ 13 C values in cap carbonates atop glacial diamictites in Paleoproterozoic strata of Wyoming and Ontario. The litho-and chemostratigraphic constraints indicate that the interval of negative carbon isotope values in well-preserved carbonates of the lower Duitschland Formation may reflect a second Paleoproterozoic ice age in the Transvaal succession. This interpretation is further supported by recently discovered bullet-shaped clasts with striations in diamictite from the basal part of the succession. Thus, the emerging temporal pattern of carbon isotope variations and glaciation in the Paleoproterozoic has a close analogue to Neoproterozoic events, suggesting a coupling of climatic and biogeochemical changes at both ends of the eon. introduction The Paleoproterozoic Era (1.6-2.5 Ga) is a distinct interval in Earth history characterized by interrelated tectonic, evolutionary, climatic, and biogeochemical events resulting in broad changes of Earth's surface environments. The detailed relationship between key transitions is poorly understood, however, due to uncertainties in correlation and the age of sedimentary successions where critical events are preserved, as well as stratigraphic omissions and post-depositional insults that obscure the true nature of temporal trends. For example, in North America, three discrete levels of Paleoproterozoic glacial diamictites are recognized in the Huronian and Snowy Pass supergroups of Ontario and Wyoming (Young, 1973, 1988; Ojakangas, 1985), respectively; on other continents only a single unequivocal diamictite of glacial origin has thus far been recognized (Ojakangas, 1985). In North America, these ice ages are radiometrically constrained to have occurred over a 230 my interval between 2.22 and 2.45 Ga (fig. 1; Krogh, Davis, and Corfu, 1984; Corfu and Andrews, 1986).
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