Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa
The Grootegeluk Formation in the Waterberg Coalfield consists of coal and mudstone layers that were deposited during the Late Permian. In the south-central part of the Waterberg Basin rapid subsidence resulted in the formation of strata (-70 m thick) which consist of relatively thin coal beds interb...
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
Department of Geological Sciences
2016
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613678042349568 |
|---|---|
| access_status_str | Open Access |
| author | Faure, Kevin |
| author2 | Willis, James |
| author_browse | Faure, Kevin Willis, James |
| author_facet | Willis, James Faure, Kevin |
| author_sort | Faure, Kevin |
| collection | Thesis |
| description | The Grootegeluk Formation in the Waterberg Coalfield consists of coal and mudstone layers that were deposited during the Late Permian. In the south-central part of the Waterberg Basin rapid subsidence resulted in the formation of strata (-70 m thick) which consist of relatively thin coal beds interbedded with a multitude of mudstone and carbonaceous mudstone layers. Mudstones from the Grootegeluk Formation, the underlying upper Vryheid Formation and the base of the overlying Beaufort Group were obtained predominantly from borehole cores. The thesis integrates thin-section petrography, mineralogy, maceral composition, maximum vitrinite reflectivity and geochemical analyses to investigate: (1) the source of the sediments and the palaeo-environment of formation of the coal and mudstone layers; (2) the stratigraphical correlations of some South African coal formations and the formation of coal, on a continental scale, during the Late Permian and Triassic times; (3) the possibility of contamination to the environment by the waste products of coal-mining ( carbonaceous mudstones) and coal-burning in a local power-station (fly ash and bottom ash). The lower portion of the Grootegeluk Formation is dominated by kaolinite, quartz and minor amounts of anatase, and the upper parts of by quartz, kaolinite and minor amounts of montmorillonite-illite and microcline. These minerals are predominantly allogenic. Mineralogical evidence from the mudstones suggests that the base of the Grootegeluk Formation was relatively more distal and the upper portions more proximal to the source of the sediments. The maceral variation of the coal seams and the organic matter in the mudstones reveal that conditions for the preservation of organic matter were more suitable during the deposition of the sediments in the upper (vitrinite-rich) rather than the lower (inertinite-rich) Grootegeluk Formation. At the base of the Grootegeluk Formation a 2 m thick carbo-tonstein occurs that is dominated by kaolinite, organic matter (-40 weight %), siderite, calcite and minor proportions of apatite. The carbo- tonstein has mineralogical, maceral and chemical characteristics distinctive from the other mudstones. Syn-depositional calcite lenses occur predominantly in the upper-half of the Grootegeluk Formation. Early diagenetic globular pyrite and spherulitic siderite occur in the coals and organic rich-mudstones of the Grootegeluk Formation. Globular pyrite and granular siderite are present predominantly in the organic-poor mudstones of the Grootegeluk Formation and Beaufort Group. Marcasite sometimes occurs along bedding planes and calcite is generally present as deat-filling in the coal seams. Based on their geochemistry, the Grootegeluk Formation and Beaufort Group mudstones have the same provenance, dominantly "granitic", possibly granodioritic in composition (Late Proterozoic Sm-Nd model ages). The provenance of the Vryheid Formation was relatively more mafic (Early Proterozoic Sm-Nd model ages). Smooth, systematic changes in the mineralogy and major element chemistry make major element whole-rod chemistry an ideal stratigraphic-indicator tool for the Grootegeluk Formation. The mudstones had very low concentrations of the alkali and alkaline-earth elements suggesting that the rocks had undergone very high degrees of chemical alteration. Trace elements in the carbonaceous mudstones are predominantly hosted in the mineral fraction. The carbo-tonstein had anomalously high concentrations of all the trace elements except S, Co, As and Zn, which, in addition to its mineralogical character, make the carbo-tonstein an important ( chrono-) stratigraphic marker for local and intra-basinal correlation. Anomalous concentrations of the chalcophile elements in the mudstones from the overlying lower Beaufort Group mudstones are considered to have been concentrated as a result of diagenesis and(or) reduction-oxidation reactions. The concentrations of trace elements and stable isotope data suggest that the sediments were deposited in fresh rather than in marine waters. Evidence from organic 13 C analyses and palynological studies indicates that ~ 13 C values can be used in stratigraphical correlations and as palaeo-ecological indicators. The ~ 13 C values of the Permian and Triassic terrestrial organic matter suggest a change in the atmospheric 13 C/1 2 C ratio during this time. Leachable concentrations of trace elements which may be toxic to plants, animals or humans are too low in coal mining discards to be of any concern. Mudstones that immediately overlie the Grootegeluk Formation coal-mudstones have leachable concentrations of elements that exceed the critical concentrations believed to be harmful to the environment. Experiments on fly ash and bottom ash samples from the Matimba power station revealed that the fly ash had unacceptably high concentrations of leachable elements, such as As, Cd and Mo. Leachates of bottom ash samples had very low concentrations of potentially harmful elements. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/21331 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:39:57.718Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Geological Sciences |
| publisherStr | Department of Geological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/21331 Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa Faure, Kevin Willis, James Geological Sciences The Grootegeluk Formation in the Waterberg Coalfield consists of coal and mudstone layers that were deposited during the Late Permian. In the south-central part of the Waterberg Basin rapid subsidence resulted in the formation of strata (-70 m thick) which consist of relatively thin coal beds interbedded with a multitude of mudstone and carbonaceous mudstone layers. Mudstones from the Grootegeluk Formation, the underlying upper Vryheid Formation and the base of the overlying Beaufort Group were obtained predominantly from borehole cores. The thesis integrates thin-section petrography, mineralogy, maceral composition, maximum vitrinite reflectivity and geochemical analyses to investigate: (1) the source of the sediments and the palaeo-environment of formation of the coal and mudstone layers; (2) the stratigraphical correlations of some South African coal formations and the formation of coal, on a continental scale, during the Late Permian and Triassic times; (3) the possibility of contamination to the environment by the waste products of coal-mining ( carbonaceous mudstones) and coal-burning in a local power-station (fly ash and bottom ash). The lower portion of the Grootegeluk Formation is dominated by kaolinite, quartz and minor amounts of anatase, and the upper parts of by quartz, kaolinite and minor amounts of montmorillonite-illite and microcline. These minerals are predominantly allogenic. Mineralogical evidence from the mudstones suggests that the base of the Grootegeluk Formation was relatively more distal and the upper portions more proximal to the source of the sediments. The maceral variation of the coal seams and the organic matter in the mudstones reveal that conditions for the preservation of organic matter were more suitable during the deposition of the sediments in the upper (vitrinite-rich) rather than the lower (inertinite-rich) Grootegeluk Formation. At the base of the Grootegeluk Formation a 2 m thick carbo-tonstein occurs that is dominated by kaolinite, organic matter (-40 weight %), siderite, calcite and minor proportions of apatite. The carbo- tonstein has mineralogical, maceral and chemical characteristics distinctive from the other mudstones. Syn-depositional calcite lenses occur predominantly in the upper-half of the Grootegeluk Formation. Early diagenetic globular pyrite and spherulitic siderite occur in the coals and organic rich-mudstones of the Grootegeluk Formation. Globular pyrite and granular siderite are present predominantly in the organic-poor mudstones of the Grootegeluk Formation and Beaufort Group. Marcasite sometimes occurs along bedding planes and calcite is generally present as deat-filling in the coal seams. Based on their geochemistry, the Grootegeluk Formation and Beaufort Group mudstones have the same provenance, dominantly "granitic", possibly granodioritic in composition (Late Proterozoic Sm-Nd model ages). The provenance of the Vryheid Formation was relatively more mafic (Early Proterozoic Sm-Nd model ages). Smooth, systematic changes in the mineralogy and major element chemistry make major element whole-rod chemistry an ideal stratigraphic-indicator tool for the Grootegeluk Formation. The mudstones had very low concentrations of the alkali and alkaline-earth elements suggesting that the rocks had undergone very high degrees of chemical alteration. Trace elements in the carbonaceous mudstones are predominantly hosted in the mineral fraction. The carbo-tonstein had anomalously high concentrations of all the trace elements except S, Co, As and Zn, which, in addition to its mineralogical character, make the carbo-tonstein an important ( chrono-) stratigraphic marker for local and intra-basinal correlation. Anomalous concentrations of the chalcophile elements in the mudstones from the overlying lower Beaufort Group mudstones are considered to have been concentrated as a result of diagenesis and(or) reduction-oxidation reactions. The concentrations of trace elements and stable isotope data suggest that the sediments were deposited in fresh rather than in marine waters. Evidence from organic 13 C analyses and palynological studies indicates that ~ 13 C values can be used in stratigraphical correlations and as palaeo-ecological indicators. The ~ 13 C values of the Permian and Triassic terrestrial organic matter suggest a change in the atmospheric 13 C/1 2 C ratio during this time. Leachable concentrations of trace elements which may be toxic to plants, animals or humans are too low in coal mining discards to be of any concern. Mudstones that immediately overlie the Grootegeluk Formation coal-mudstones have leachable concentrations of elements that exceed the critical concentrations believed to be harmful to the environment. Experiments on fly ash and bottom ash samples from the Matimba power station revealed that the fly ash had unacceptably high concentrations of leachable elements, such as As, Cd and Mo. Leachates of bottom ash samples had very low concentrations of potentially harmful elements. 2016-08-18T13:52:42Z 2016-08-18T13:52:42Z 1993 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/21331 eng application/pdf Department of Geological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Geological Sciences Faure, Kevin Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa |
| thesis_degree_str | Doctoral |
| title | Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa |
| title_full | Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa |
| title_fullStr | Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa |
| title_full_unstemmed | Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa |
| title_short | Mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the Grootgeluk formation in the Waterberg coalfield, South Africa |
| title_sort | mineralogy and geochemistry of the carbonaceous mudstones and coal petrogenesis of the grootgeluk formation in the waterberg coalfield south africa |
| topic | Geological Sciences |
| url | http://hdl.handle.net/11427/21331 |
| work_keys_str_mv | AT faurekevin mineralogyandgeochemistryofthecarbonaceousmudstonesandcoalpetrogenesisofthegrootgelukformationinthewaterbergcoalfieldsouthafrica |