The petrographic composition of Cretaceous-age coals hosted in the Benue Trough,Nigeria is presented and discussed in terms of the paleodepositional settings that infuenced the coal-bearing formations.The Benue Trough...The petrographic composition of Cretaceous-age coals hosted in the Benue Trough,Nigeria is presented and discussed in terms of the paleodepositional settings that infuenced the coal-bearing formations.The Benue Trough is a failed arm of the triple junction of an inland sedimentary basin that extends in a NE-SW direction from the Gulf of Guinea in the south,to the Chad Basin in the north.A total of twenty-nine(29)coal samples were obtained from nineteen coal localities in the Upper(UBT),Middle(MBT),and Lower Benue Trough(LBT).The high average volatile matter yield,low average ash yield,high calorifc value(24.82 MJ/kg,on average),and low sulphur values indicate good quality coal deposits.The organic matter is dominated by vitrinite,reported at an average of 59.3%by volume(mineral-matter free).Variation was noted in the inertinite content across three sub-regions.Liptinite macerals were not commonly observed in the studied samples and were absent in the MBT samples.Coal facies studies decipher the paleoenvironmental conditions under which the vegetation accumulated.Indices commonly used are the gelifcation index(GI),tissue preservation index(TPI),ground water index(GWI and variations),vegetation index(VI),and wood index(WI).Comparing the array of coal facies models applied,the MBT samples difer from the UBT and LBT samples,concurring with the coal quality data.The UBT and LBT coals formed in an upper deltaic to drier piedmont plane depositional environment,while the MBT coal formed in a lower deltaic marsh to wet forest swamp depositional environment.All samples indicate an ombrotrophic paleomire.In view of the modifed equations and the plots used,interpreting depositional environments from just a single model is not reliable.展开更多
This study investigates the paleodepositional conditions of the No.6 Seam of the Madzaringwe Formation in Makhado and Voorburg south area of the Soutpansberg Coalfield(Limpopo Province,South Africa)utilizing organic p...This study investigates the paleodepositional conditions of the No.6 Seam of the Madzaringwe Formation in Makhado and Voorburg south area of the Soutpansberg Coalfield(Limpopo Province,South Africa)utilizing organic petrography and inorganic geochemical proxies.The coals are predominantly high-volatile bituminous B-A rank with high ash yields(avg.36.1 wt%),characterized by high-vitrinite(~41.5 vol%),moderate-to-high inertinite(9.8 vol%–33.7 vol%)and low liptinite(~2.3 vol%).The distribution of inertinite varies among different coal horizons(from bottom-lower to middle-upper),suggesting differential oxidation conditions and/or paleofire occurrence.Vitrinite-to-inertinite(V/I)ratio,tissue preservation–gelification index(TPI–GI),and groundwater–vegetation index(GWI–VI)plots,indicate that the peat-forming forest-swamp vegetation accumulated under mesotrophic-to-rheotrophic hydrological conditions.The presence of structured macerals(i.e.,telinite,collotelinite,fusinite,and semifusinite)suggests well-preserved plant tissues,whereas framboidal pyrite and sulphur content(0.24 wt%–2.16 wt%)point to brackish-water influence at the peat stage.The coals contain quartz,kaolinite,siderite,muscovite,dolomite,calcite,and pyrite minerals,most of which were likely sourced from felsic igneous rocks.The Al/(Al+Fe+Mn)and(Fe+Mn)/Ti ratios for the studied samples range between 0.24–0.97 and 0.57–70.10,respectively.The ratios,Al–Fe–Mn plot,and presence of massive botryoidal-type pyrite imply some influence of meteoric waters or fluids from hydrothermal activity post-deposition.Moreover,the chemical index of alteration(CIA:98.25–99.67),chemical index of weathering(CIW:92.04–97.66),and A–CN–K ternary diagram suggest inorganic matter suffered strong chemical weathering,indicating warm paleoclimatic conditions during the coal formation.展开更多
Dyke swarms are widespread throughout the Kaapvaal Craton(KC)in South Africa and have been documented in some detail.Up to date,only the^2.9 Ga SE-trending and the^2.7 to^2.66 Ga radiating dyke arrays are
Coal-fired power plants (CFPP) provide approximately 40% of the world’s energy demand. Naturally occurring radioactive materials (NORM) contained in coal become enriched in coal combustion residues as a result of the...Coal-fired power plants (CFPP) provide approximately 40% of the world’s energy demand. Naturally occurring radioactive materials (NORM) contained in coal become enriched in coal combustion residues as a result of the elimination of carbon during combustion. The fly ash and bottom ash produced from CFPP may be significant sources of exposure to naturally occurring radionuclides for the population near the combustion plant or ash dumps. Despite this fact, very few studies have actually addressed the relationship of the NORM enrichment factors and the quality of coal used. This paper aims to relate the quality of coal to the enrichment factors for the radionuclides of interest (K40, Ra226, Th232 and Po210) in coal combustion residues from three South African CFPP. The data from other CFPP was also taken into account to establish this correlation. The feedstock coal used in these CFPP is typically low quality, with ash content in the range of 25 - 45 wt%. The radionuclides investigated were determined by gamma spectrometry with the exception of Po210, which was determined by alpha spectrometry. The enrichment factors for the radionuclides of K40, Ra226, Th232 and Po210 in the fly ash and bottom ash (except Po210) was found to be directly proportional to the quality of coal. That is when the ash percentage increased (coal quality decreased) the enrichment factor decreased. The Po210 radionuclide in the bottom ash had an enrichment factor less than one. The relationship between coal quality and enrichment factors for the radionuclides of K40, Ra226, Th232 and Po210 in both the fly ash and bottom ash (except Po210 in the bottom ash) was demonstrated by the following mathematical equation: . This equation may be used as a good indication in obtaining an estimate in determining the enrichment of the mentioned radionuclides in coal combustion products such as fly ash and bottom ash.展开更多
Africa hosts just over 80 percent(%)of the world’s known land-based ore resources of manganese metal and produced some 41.1%of the 18 million tonnes(Mt)of manganese metal in ores,that was mined during 2014.The deposi...Africa hosts just over 80 percent(%)of the world’s known land-based ore resources of manganese metal and produced some 41.1%of the 18 million tonnes(Mt)of manganese metal in ores,that was mined during 2014.The deposits are mainly of sedimentary and supergene origin comprising four major types,namely banded iron formation(BIF)-hosted,black shale-hosted,oolitic and supergene/karst-hosted deposits.展开更多
基金The support of the Department of Science and Innovation through its funding agency,the National Research Foundationthe Centre of Excellence for Integrated Mineral and Energy Resource Analysis(DSI-NRF CIMERA)towards this research is hereby acknowledged.
文摘The petrographic composition of Cretaceous-age coals hosted in the Benue Trough,Nigeria is presented and discussed in terms of the paleodepositional settings that infuenced the coal-bearing formations.The Benue Trough is a failed arm of the triple junction of an inland sedimentary basin that extends in a NE-SW direction from the Gulf of Guinea in the south,to the Chad Basin in the north.A total of twenty-nine(29)coal samples were obtained from nineteen coal localities in the Upper(UBT),Middle(MBT),and Lower Benue Trough(LBT).The high average volatile matter yield,low average ash yield,high calorifc value(24.82 MJ/kg,on average),and low sulphur values indicate good quality coal deposits.The organic matter is dominated by vitrinite,reported at an average of 59.3%by volume(mineral-matter free).Variation was noted in the inertinite content across three sub-regions.Liptinite macerals were not commonly observed in the studied samples and were absent in the MBT samples.Coal facies studies decipher the paleoenvironmental conditions under which the vegetation accumulated.Indices commonly used are the gelifcation index(GI),tissue preservation index(TPI),ground water index(GWI and variations),vegetation index(VI),and wood index(WI).Comparing the array of coal facies models applied,the MBT samples difer from the UBT and LBT samples,concurring with the coal quality data.The UBT and LBT coals formed in an upper deltaic to drier piedmont plane depositional environment,while the MBT coal formed in a lower deltaic marsh to wet forest swamp depositional environment.All samples indicate an ombrotrophic paleomire.In view of the modifed equations and the plots used,interpreting depositional environments from just a single model is not reliable.
文摘This study investigates the paleodepositional conditions of the No.6 Seam of the Madzaringwe Formation in Makhado and Voorburg south area of the Soutpansberg Coalfield(Limpopo Province,South Africa)utilizing organic petrography and inorganic geochemical proxies.The coals are predominantly high-volatile bituminous B-A rank with high ash yields(avg.36.1 wt%),characterized by high-vitrinite(~41.5 vol%),moderate-to-high inertinite(9.8 vol%–33.7 vol%)and low liptinite(~2.3 vol%).The distribution of inertinite varies among different coal horizons(from bottom-lower to middle-upper),suggesting differential oxidation conditions and/or paleofire occurrence.Vitrinite-to-inertinite(V/I)ratio,tissue preservation–gelification index(TPI–GI),and groundwater–vegetation index(GWI–VI)plots,indicate that the peat-forming forest-swamp vegetation accumulated under mesotrophic-to-rheotrophic hydrological conditions.The presence of structured macerals(i.e.,telinite,collotelinite,fusinite,and semifusinite)suggests well-preserved plant tissues,whereas framboidal pyrite and sulphur content(0.24 wt%–2.16 wt%)point to brackish-water influence at the peat stage.The coals contain quartz,kaolinite,siderite,muscovite,dolomite,calcite,and pyrite minerals,most of which were likely sourced from felsic igneous rocks.The Al/(Al+Fe+Mn)and(Fe+Mn)/Ti ratios for the studied samples range between 0.24–0.97 and 0.57–70.10,respectively.The ratios,Al–Fe–Mn plot,and presence of massive botryoidal-type pyrite imply some influence of meteoric waters or fluids from hydrothermal activity post-deposition.Moreover,the chemical index of alteration(CIA:98.25–99.67),chemical index of weathering(CIW:92.04–97.66),and A–CN–K ternary diagram suggest inorganic matter suffered strong chemical weathering,indicating warm paleoclimatic conditions during the coal formation.
基金financial support from the PPM Research Group and CIMERA in South Africa
文摘Dyke swarms are widespread throughout the Kaapvaal Craton(KC)in South Africa and have been documented in some detail.Up to date,only the^2.9 Ga SE-trending and the^2.7 to^2.66 Ga radiating dyke arrays are
文摘Coal-fired power plants (CFPP) provide approximately 40% of the world’s energy demand. Naturally occurring radioactive materials (NORM) contained in coal become enriched in coal combustion residues as a result of the elimination of carbon during combustion. The fly ash and bottom ash produced from CFPP may be significant sources of exposure to naturally occurring radionuclides for the population near the combustion plant or ash dumps. Despite this fact, very few studies have actually addressed the relationship of the NORM enrichment factors and the quality of coal used. This paper aims to relate the quality of coal to the enrichment factors for the radionuclides of interest (K40, Ra226, Th232 and Po210) in coal combustion residues from three South African CFPP. The data from other CFPP was also taken into account to establish this correlation. The feedstock coal used in these CFPP is typically low quality, with ash content in the range of 25 - 45 wt%. The radionuclides investigated were determined by gamma spectrometry with the exception of Po210, which was determined by alpha spectrometry. The enrichment factors for the radionuclides of K40, Ra226, Th232 and Po210 in the fly ash and bottom ash (except Po210) was found to be directly proportional to the quality of coal. That is when the ash percentage increased (coal quality decreased) the enrichment factor decreased. The Po210 radionuclide in the bottom ash had an enrichment factor less than one. The relationship between coal quality and enrichment factors for the radionuclides of K40, Ra226, Th232 and Po210 in both the fly ash and bottom ash (except Po210 in the bottom ash) was demonstrated by the following mathematical equation: . This equation may be used as a good indication in obtaining an estimate in determining the enrichment of the mentioned radionuclides in coal combustion products such as fly ash and bottom ash.
文摘Africa hosts just over 80 percent(%)of the world’s known land-based ore resources of manganese metal and produced some 41.1%of the 18 million tonnes(Mt)of manganese metal in ores,that was mined during 2014.The deposits are mainly of sedimentary and supergene origin comprising four major types,namely banded iron formation(BIF)-hosted,black shale-hosted,oolitic and supergene/karst-hosted deposits.
