GEOCHEMICAL AND MINERALOGICAL CHARACTERIZATION OF THE LITHOLOGICAL UNITS OF THE GEODEHOOP COLLIERY IN THE WITBANK COALFIELD TO FATHOM THE SOURCE AND THE RECEPTOR OF METALS IN THE RIET-OLIFANTS CATCHMENT, SOUTH AFRICA By Khashane Robert Tshishonga Netshitungulwana Bachelor of Earth Science (UNIVEN), MSc (Geology) (UFS) Supervisor: Prof. Christoph Gauert Geological Survey of Saxony-Anhalt, Department of Applied Geoscience, An der Fliederwegkaserne 13, 06130 Halle (Saule), Germany Co-Supervisor: Prof. Danie Vermeulen Institute for Ground Water Studies, University of the Free State, 205 Nelson Mandela Drive, Parkwest, Bloemfontein, 9300 Co-Supervisor: Prof. Bisrat Yibas University of the Free State, Faculty of Natural and Agricultural Sciences, Department of Geology, 205 Nelson Mandela Drive, Parkwest, Bloemfontein, 9300 i | P a g e DECLARATION The contents of this dissertation are the result of my doctoral research at the University of the Free State. This work has never been submitted for a degree at this or any other institution. The work of others is acknowledged through citations. _______________________________________ T.K.R. Netshitungulwana Department of Geology University of the Free State 30th November 2022 i | P a g e PREFACE This thesis was written as the author's doctoral dissertation at the University of the Free State. The study was conducted in the Witbank coalfield restricted to the ROC, a sub catchment of the OPC, which is located on the western side of Mpumalanga Province, and consists of the towns of Emalahleni, Middleburg, Kriel, Hendrina, Bethal, and Arnot. Understanding the fate of metals from their geological source to the receiving environment is the primary objective of this study. Understanding the processes for metal receipt in water streams from anthropogenic and/or geogenic sources and developing techniques for mitigation and, if feasible, avoidance of the increasing element load are the intents of the present work. It is also meant to stimulate a discussion on the possibility of amending section 36 of the Mineral and Petroleum Resources Development Act No. 28 of 2008 and section 24 (1) of the National Environment Management Act of 1998, in order to compel the characterization of geological units and receptor realm, to be encountered during exploitation, prior to the granting of mining rights to a potential applicant. The study has achieved its objective, highlighting that characterization of the lithogical units, receptor realm, and understanding of the deportment processes can be used to assign a potential source of metals in the receptor environment. The wastes resulting from the lithological units, can be classified according to the level of management required, and allow metal input in the receptor realm that does not exceed the determined standards. Continuous monitoring has been highly recommended. The author studied part-time at the University of the Free State for more than five years. The first three years of the project were devoted to data mining, fieldwork, and analysis. Humidity cell leach, a kinetic test of 31 weeks had been conducted at the fifth year. The study was presented abroad, resulting in 3 peer-reviewed papers and 1 book chapter (referenced); further publications are expected. The author supervised and directed MSc project under restricted promoter monitoring as part of the learning process for autonomous scientific activity. This text contains the subsequent chapters: 1) introduction; 2) geological setting of ROC; 3) petrography and geochemistry of the source rock; 3) mine drainage: case study Geodehoop colliery; 5) stream sediments geochemistry; 6) summary and recommendations; 7) waste management framework guideline proposal. ii | P a g e ACKNOWLEDGEMENT Professor Christopher Gauert (UFS), Professor D. Vermeulen (UFS), and Professor B. Yibas (UFS) have provided me with the opportunity to study at the University of the Free State. They have guided and encouraged me throughout my years of study. Special thanks are due to Dr Lore-Mari Deysel and Ms Matamela Madzonga of the University of the Free State for their diligent labor on the 31-week humidity cell leach test experiment and weekly analysis, and Ms Raleaka Moshia at CGS for sample preparation. I am indepted to Mr Peter Roberts, a principal geologist at Anglo American Thermal Coal, for donating the borehole cores (ZFN1510 and ZFN1512). I am indebted to the leading MSc candidates, Mr Mateo Shai and Ms Matamela Madzonga, for their arduous efforts to complete their respective projects. Mr Mateo Shai labored extensively to complete his MSc, a part of which is shown in chapter 3. The late Mr Ntshengedzeni Obed Novhe and Mr Rudzani Lusunzi from the Council for Geoscience for sharing their broad knowledge of environmental geochemistry, emphasing on mine drainage. I am indebted to the following individuals from Council for Geoscience: Ms M. Crowley for her support with XRF analysis, Ms N. Dlamini for her aid with XRD analysis, and Dr N. Malumbazo and her team for their assistance with coal analysis. I want to thank Prof D. Vermeulen from the University of the Free, Institute for Groundwater Studies department for sponsoring the 31-week humidity cell analytical experiment with full support. I am very grateful to be part of the Council for Geoscience family led by Mr Mosa Mabuza, who offered their full support on the project's funding from start to finish. By expressing thanks to the Council for Geoscience and the University of the Free State, I am beholden to thank the South Africans for allowing me to contribute at the highest level of education and add in providing the solutions that trouble our country, like mine drainage. It is a piece of public knowledge that water is a scarce resource in South Africa. If contaminated, it also threatens the socio-economic development of the country. It is, therefore, essential to protect and preserve this resource for the future generations of our people. Mr J.H. Elsenbroek, the late Mr S. Strauss, the late Mr E.M. Nkosi, Mr A.E. Mulovhedzi, Dr V. Nxumalo, Mr S. Hlatshwayo, Mr K. Nedzingahe, Mr M. Bensid, and Dr T. Dansay (Manager: Minerals and iii | P a g e Energy Unit) are all thanked for their moral support and encouragement, as well as for sharing their extensive knowledge of exploration geochemistry. This dissertation is a testament to my family that future generations will cherish: my wife, Tendani Shumani; my children, Ndiene Mukundi, Mulanga Vhuthuhawe, Wamashudu Tshamaano, Tendani, Mpho, Adivhaho, Khavharendwe, Muruli, Murunwa, Orita, and Thimulitshi; my parents, mothers include Marubini Mercy, Christinah, Grace, and Violet, and my father Tshamaano David Philemon. I am grateful to my parents and the rest of my family for believing in me through thanksgiving prayers to Yahavee, persistence and support in my academic pursuits. This thesis would be the paper tying our grandkids to us and future generations. I hope that our family will continue to serve the people of the planet in which we reside. Praise “Yahavee” the creator, who has shown compassion for humanity by giving hope to the rejected. “Yahavee” have shown mercy in all my lacks and forgiven me, and I sincerely believe in the greatest sacrifice, “Yeshua the Messiah”. I am indebted to the late Rev M.P. Kruger and his family for their upbringing and guidance. Rev N. Mundalamo for his ceaseless prayers, constant guidance, and availability with the entire Reformed Church, Synod Soutpansberg family. Regarding the time of my studies, I would like to thank Mr Nndwakhulu Tshishonga in UKZN and his family in Cape Town for their tremendous emotional support and encouragement. Netshitungulwane-Tshishonga-Mundalamo: Tshitungulwane tsha Mapfulagatsha-zhinda la Tshishonga Lugongolo, muduhulu wa Dimbanyika, le la wela mulambo wa Luvuvhu na Mabadahanya, Muila na Mmbooi la yo thukha thavhani dza Tshitee, Lumawe, Musukhomu, Madzivhanombe, Tshivhulani, Tshilaphala, Mpaladzi, Tshiendeulu na dzinwe. Mapfulagatsha, mapfula misevhe wa tshanda tsha danda tsha u pfula vhathu na phukha. Tshitungulwane tsha Mangumane, Tshitungulwane tsha Khashane, Tshitungulwane tsha Muvhi, Tshitungulwane tsha Makwarela, ane vha tshi murenda vhe “Makwarela pesa la nwenda line la kheruwa, ri a tanganya”. Tshitungulwane tsha Piet-Mawelewele; Ntavhanyeni Johannes; Mufhiri-William; Rasiwela-Jackson; Fhedzisani-Simon; Tshamaano (Tambaulate); Erasmus-Mundalamo; Ntshavheni-Ntsieni. Muila mutshila wa mbudzi. iv | P a g e EXECUTIVE SUMMARY The study aims to understand the element deportment's geochemical characteristics from the source, pathway and receptor realm in the Riet-Olifants catchment (ROC) drainage system. The ROC is part of the Olifants primary catchment (OPC) area that extends over the border between South Africa and Mozambique and covers a total area of approximately 87000 km2. The ROC is the area most influenced by coal mining activities surrounding the major towns of Emalahleni (formerly Witbank) and Middleburg. The geological units of the Vryheid Formation, Ecca Group of the Karoo Supergroup dominate the area, with the Witbank coalfield being the primary resource for coal. The focus herein is directed on identifying the geochemical characteristics of the source rocks, the pathways of mobilization and transport and the receiving environment. The key to this study is to identify the mobile elements in minerals occurring in different sedimentary units of the source rock geological units, with the assessment of its contribution to the elevated metal concentrations in the receiving environment of the drainage area. The results are also tested in determining the geogenic element entry of naturally occurring source rocks from an anthropogenic source. In recent years, the area has been under regulatory verification over high pollution levels through coal mine drainage (MD). Previous studies show that although the land use of industrial and agricultural activities is also essential, the contribution to water and sediment contamination from the mining activities within the catchment is significant and yet needs to be fully understood. The lithological units of the Witbank coalfield consist of sandstones, coal, shale, dolerite, tillites, and basement granite. Coal seams contain the following minerals: kaolinite, quartz, pyrite, calcite, dolomite, siderite, anatase, and mica. Notably, the pyrite content in coal ranges from 4 to 51 wt.%. Sandstones/siltstones and shales make up the hanging and footwalls of coal seams. Clay group (kaolinite/chlorite, smectite), carbonates group (calcite, dolomite, and siderite), quartz, potassium feldspar, plagioclase, pyrite, mica minerals, hematite, anatase as an accessory. The classification schemes of terrigenous shales and sandstones using Fe2O3/K2O vs SiO2/Al2O3 reveals that the majority of the sediments are shales with minor Fe-rich, arkose with minor subarkose, wacke and minor litharenite. v | P a g e The ABA and kinetic test of lithological units were used to determine the MD generating potential. A total of 65 samples were assessed represented by borehole ZFN1510. The samples were assessed based on the NPR vs. Sulphur, NNP vs. paste pH and AP vs. NP. With the exception of coal seam number 5, coal seams 4, 3 and 2 can generate acid MD. Coal seam number 5 contains an excess of carbonate minerals, making up 19% of its modal mineralogy. The shale units and sandstones above or below the coal seams are classified into areas with acid MD production uncertainty. These units have the potential to strongly increase the acid generation while excess carbonates minerals act as a buffer in the process. The humidity cell leach test confirms a continuous leaching of metals during the 31-week experiment, modelled over 100 years. The reaction processes involved in the transportation of elements include but not limited to: sulphide oxidation, acid neutralization and alkalinity, ion exchange or adsorption, precipitation metal hydroxides and salts, and hydrolysis. Metal influxes and effluxes from GWB and calculated metal loads (mg.kg-2.yr) reveals that the metal contributions to the receptor realm is largely from the coal seams and above or below lithological units. A total of 246 stream sediments samples were collected to represent the receiving environment at a scale of three samples per 10 km2 to assess metal accumulation. The bedrock geology partly controls the downstream sediment geochemistry. The major elements of Ca, Na, K, and Mg, are enriched in the stream sediments due to their mobility as they are leached, transported and precipitated. The trace elements of As, Br, Co, Hf, Nb, Nd, Ni, Se, Sm, Ta, Pb, Zn, U, V and Yb are also enriched in the stream sediments. Pb, Zn, As, and U exhibit abnormal concentrations in Karoo sandstones, and probability plots of element concentrations indicate multiple populations, which may indicate a geogenic input. Positive correlations exist between U and Nd, Nb, W, Hf, Br, Se, Yb, Cs, and Co, whereas As has a significant relationship with Sm, Ta, Mo, Ge, Pb, Cs, and Zn. Elements with high aqueous mobility towards the sedimentary sink, such as Pb and Zn, each with an enrichment factor (EF) greater than 1.5, show a significant correlation with Ta, Mo, and Ge. Pb and Zn are very valuable for recognizing the human effect on a river, such as urban runoff and mining input. However, their EF implies a nearby geological origin. Certainly, As, Pb, Cd, Tl, and other metals are derived from the biological content of the coal seams when they are leached by mining. vi | P a g e The bedrock contribution, also on average, in the study area to the average downstream sediment concentrations can be qualified. The possible coal seam, above and below lithological units's contributions to the downstream sediment geochemistry include Ca, Na, K, Mn, Mg and SO4 2- (also contributions by chalcophile elements such as As, Fe, Cu and Zn). The large quantity of these elements is from the coal seams. As, shows a significant increase from the maximum value of 36 ppm on average bedrock to the maximum of 680 ppm in average stream sediment. The possible source of the hanging and footwall of the coal seams include U from the maximum concentrations of 11 ppm in the average bedrock to 1898 ppm in the average stream sediments. Pb in the hanging and footwall of the coal seam shows significant concentrations increase from the maximum concentrations of 38 ppm on average bedrock to 98 ppm in average stream sediments. The other elements, which are possibly sourced from a mafic source include V, Cr and Co as reflected by the significant increase of concentrations from the maximum value of 489 ppm, 189 ppm, 42 ppm in average bedrock to the maximum value of 1028 ppm, 3207 ppm, 1273 ppm in average stream sediments, respectively. The latter mafic element input in the streams may be anticipated for base metals and steel refining metals, for anthropogenic input. The source, pathway and receiving environment approach adopted herein representing the ROC aims at achieving the objectives set in this study has been successful. To ensure minimal contamination, it is necessary to group materials with similar geochemical properties, as some may demand a greater level of treatment than others. vii | P a g e LIST OF FIGURES Figure 1-1: A map of the research region, the ROC, Mpumalanga Province highlighted in blue. ................. 4 Figure 1-2: A map showing a location for the OPC area, South Africa. ........................................................ 6 Figure 1-3: Simplified conceptual model highlighting the sources pathways and receptor environment for the metals............................................................................................................................................................ 11 Figure 1-4: The mine drainage chemical prediction wheel (adapted from Morin and Hutt, 1999). ............. 12 Figure 2-1: The regional geological map of the ROC. ................................................................................. 14 Figure 2-2: Generalized stratigraphic columns of the Witbank coalfield (after Smith and Whittaker, 1986).16 Figure 2-3: A map showing the approximate position (shown by an arrow) of the Geodehoop boreholes ZFN1510 and 1512 project at Zondagfontein farm close to the ROC catchment devide, as well as the Goedehoop Colliery in the Zondagfontein project area and Witbank coalfield cross-section with seams No. 1–5 (after Graham and Lategan, 1931a). ........................................................................................................................................... 24 Figure 3-1: The sampled stratigraphic units of the Zondagsfontein project (Geodehoop colliery) from Anglo Coal Pty.Ltd. ......................................................................................................................................................... 28 Figure 3-2: Witbank coalfied metasediments compositions for BH1510 and 1512 (valid N = 123) in the classification schemes of terrigenous shales and sandstones using Fe2O3/K2O vs SiO2/Al2O3 by Herron (1988) after Gauert (2005). ..................................................................................................................................... 35 Figure 3-3: A dolerite sample represented by M30 exhibits plagioclase, clinopyroxene, and potassium feldspar phenocryst with orthoclase twining in A; quartz, elongated plagioclase, and carbonates minerals in B; and elongated phenocryst of plagioclase with albite twining in C. ..................................................................... 39 Figure 3-4: Shale represented by sample M28 exhibiting framboidal pyrite grains in A and showing quartz, mica, plagioclase and chlorite in B under crossed-polarised transmitted light. ...................................................... 40 Figure 3-5: Sandstone represented by sample M33 exhibits spongy pyrite in A, and quartz, mica, kaolinite and plagioclase in B under crossed-polirased transmitted light. ......................................................................... 40 Figure 3-6: The seam No. 5 represented by sample M35 exhibits kaolinite, quartz, and mica in A, and pyrite elongation in B, under reflected light. .......................................................................................................... 41 Figure 3-7: A framboidal pyrite in A under reflected light; potassium feldspar and quartz in B, and displaying potassium feldspar and quartz in carbonates and muscovite matrix of sandstone represented by sample M41. ...................................................................................................................................................................... 42 Figure 3-8: Coal seam No. 4 represented by sample M44 display spongy pyrite under a reflected light. .... 43 Figure 3-9: Quartz grains showing pyrite matrix under reflected light in B. ................................................ 43 Figure 3-10: Coal seam No. 3 represented by sample M53 exhibiting vein fillings of pyrite in A and spongy pyrite in B under a reflected light. ................................................................................................................ 44 Figure 3-11: The spongy pyrite in A and spongy pyrite with inertinite and vitrinite in B under reflected light. ...................................................................................................................................................................... 44 viii | P a g e Figure 3-12: Dwyka tillite represented by sample M64 under transmitted light exhibiting plagioclase notably albite twining, potassium feldspar, quartz and muscovite in A; grains of quartz notably clastic in B. ........ 45 Figure 3-13: Granite reprented by sample M65 presenting muscovite (Ms) altering to chlorite and intersertal or granophyric intergrowth of feldspar and quartz in A; and also showing plagioclase notably albite twining, potassium feldspar and quartz in B. .............................................................................................................. 46 Figure 3-14: Borehole profiles indicate the large quantity of major elements (in weight percent) at the Geodehoop Colliery, Witbank coalfield. ......................................................................................................................... 49 Figure 3-15: Borehole profile showing the large quantity of elements C, S, and LOI (in weight percent) and Co, Ni, Cu, and V (ppm) at the Geodehoop mine, Witbank coalfield. ................................................................ 52 Figure 3-16: Depicts fluctuation profiles of trace element large quantity (ppm) in the Witbank Coalfield.. 53 Figure 3-17: Profile variation plots illustrating the large quantity of key minerals (kaolinite, kaolinite/chlorite, mica, anatase, and smectite, in weight percent) in the Witbank coalfield. ................................................... 54 Figure 3-18: Profile variation plots showing an large quantity of major minerals (kaolinite, kaolinite/chlorite, mica, anatase and smectite in wt.%) in the Witbank coalfield. .................................................................... 59 Figure 3-19: Profile variation plots showing major minerals (carbonates, quartz, feldspar and pyrite in wt %) in wt.%, in the Witbank coalfield. .................................................................................................................... 60 Figure 4-1: Acid base accounting static test pre-assessments using NPR vs Sulphur content in weight %. 74 Figure 4-2: Acid base accounting static test pre-assessments using NNP vs Paste pH classification. ......... 75 Figure 4-3: Acid base accounting static test pre-assessments using AP vs. NP classification. .................... 75 Figure 4-4: Generic schematic layout for the arrangement of a humidity cell leach (Mills, 1998), as well as an HCL test at the IGS University of the Free State. ........................................................................................ 83 Figure 4-5: Presents a graphical representation of the pH results of the humidity cell leaching 31 week experiments. ................................................................................................................................................. 87 Figure 4-6: Shows a graphical representation of the SO4 2- (mg/L) concentrations in the leachate of the humidity cell leach 31 week tests. ............................................................................................................................... 87 Figure 4-7: Graphical summary statistics of leachate Alkalinity values of the humidity cell leach 31 week tests. ...................................................................................................................................................................... 88 Figure 4-8: Graphical summary statistics of leachate SO4 2- (mg/L) concentrations of the humidity cell leach 31 week tests. .................................................................................................................................................... 88 Figure 4-9: The Humidity leach test indicating metal release rate of SO4 2-, EC, Ca, Mg, Na and K per week for BH10 and BH19. .......................................................................................................................................... 91 Figure 4-10: The Humidity leach test indicating for SO4 2-, EC, Ca, Mg, Na and K per week of BH4 and BH20. ...................................................................................................................................................................... 92 Figure 4-11: The Humidity leach test indicating metal release rate of SO4 2- (mg/L), EC (mS/m), Ca (mg/L), Mg (mg/L), Na (mg/L) and K (mg/L) per week of BH11 and BH21 for coal seam No 4. ................................. 94 Figure 4-12: The Humidity leach test indicating metal release rate of SO4 2- (mg/L), EC (mS/m), Ca (mg/L), Mg (mg/L), Na (mg/L) and K (mg/L) per week of BH12 and BH24 for coal seam No. 3. ................................ 95 ix | P a g e Figure 4-13: The Humidity leach test indicating metal release rate of SO4 2- (mg/L), EC (mS/m), Ca (mg/L), Mg (mg/L), Na (mg/L) and K (mg/L) per week of BH7 and BH26 rock units between coal seam No. 3 and 2. 96 Figure 4-14: The Humidity leach test indicating metal release rate of SO4 2- (mg/L), EC (mS/m), Ca (mg/L), Mg (mg/L), Na (mg/L) and K (mg/L) per week of BH6 and BH23 for rock units below coal seam No. 3. ....... 97 Figure 4-15: The Humidity leach test indicating metal release rate of SO4 2- (mg/L), EC (mS/m), Ca (mg/L), Mg (mg/L), Na (mg/L) and K (mg/L) per week of BH13 and BH26 for coal seam No. 2. ................................ 98 Figure 4-16: The Humidity leach test indicating metal release rate of SO4 2- (mg/L), EC (mS/m), Ca (mg/L), Mg (mg/L), Na (mg/L) and K (mg/L) per week of BH1. .................................................................................... 99 Figure 4-17: The Humidity leach test indicating metal release rate of SO4 2- (mg/L), EC (mS/m), Ca (mg/L), Mg (mg/L), Na (mg/L) and K (mg/L) per week of BH2 and BH3.................................................................... 100 Figure 4-18: The Humidity leach test indicating metal release rate of SO4 2- (mg/L), EC (mS/m), Ca (mg/L), Mg (mg/L), Na (mg/L) and K (mg/L) per week of BH8 and BH9.................................................................... 101 Figure 4-19: General stability diagram from GWB at temperature = 25oC, pressure = 1.013 bars for elements Ba, Ca, Sr, Si, SO4 2-, Al, Mn and Mg. .............................................................................................................. 105 Figure 4-20: Saturation index of species of barite and anhydrite versus the SO4 2- contrations in mg/L in the leachate. ...................................................................................................................................................... 108 Figure 4-21: Saturation index of species of celestine and CdSO4 (hawleyite, greenockite) versus the SO4 2- contrations in mg/L in the leachate. ............................................................................................................ 109 Figure 4-22: Saturation index of species of gypsum versus the SO4 2- contrations in mg/L in the leachate. 110 Figure 4-23: Sulphate cumulative representation over 31 week HCL experiment for coal seam No. 2. .... 111 Figure 4-24: Sulphate cumulative representation over 31 week HCL experiment for coal seam No. 4. .... 112 Figure 4-25: Sulphate cumulative representation over 31 week HCL experiment for coal seam No. 5 ..... 112 Figure 4-26: Sulphate cumulative representation over 31 week HCL experiment for coal seam No. 5. .... 113 Figure 4-27: Kinetic reative model for 100 years the ZFN1512 and ZFN1510 coal units. ........................ 116 Figure 4-28: Piper diagram for the cumulative leachate for the ZFN1512 and ZFN1510 coal units, symbols indicates changes in composition at different nodes................................................................................... 117 Figure 4-29: Bar chart for cumulative representation for cations and anions modelled for 100 years in coal seams. .................................................................................................................................................................... 118 Figure 4-30: Kinetic reative model for 100 years the ZFN1512 and ZFN1510 A-B (above and below) units.120 Figure 4-31: Piper diagram for the cumulative leachate for the ZFN1512 and ZFN1510 for above and below units, symbols indicates changes in composition at different nodes. ................................................................... 121 Figure 4-32: Bar chart for cumulative representation for cation and anion modelled for 100 years in above and below coal seams units. .............................................................................................................................. 122 Figure 4-33: A total of 31 weeks cumulative concentrations of Fe and SO4 2- of the coal seams marked by BH 10, 11, 12, 13 and 19. ....................................................................................................................................... 125 Figure 4-34: A total of 31 weeks cumulative concentrations of SO4 2- and Total alkalinity of the coal seams marked by BH 10, 11, 12, 13 and 19. ...................................................................................................................... 126 x | P a g e Figure 4-35: A total of 31 weeks cumulative concentrations of Mg and Ca of the coal seams marked by BH 10, 11, 12, 13 and 19. ....................................................................................................................................... 127 Figure 4-36: A total of 31 weeks cumulative concentrations of Ca and Na of the coal seams marked by BH 10, 11, 12. ......................................................................................................................................................... 128 Figure 4-37: ROC indicating the locations of the mines. ........................................................................... 130 Figure 4-38: Mines occurences proximity to the ROC. .............................................................................. 130 Figure 4-39: Figure indicating paleochannel as traps showing the a larger part of the southern streams of the area are running in former palaeochannels in the ROC...................................................................................... 131 Figure 5-1: The ROC simplified geological map, distribution of sample locations, and placement of coal mines (the study area). .......................................................................................................................................... 136 Figure 5-2: Presents a statistical overview of Al2O3 concentrations........................................................... 147 Figure 5-3: Summary statistics of Al2O3 concentrations. ........................................................................... 148 Figure 5-4: Summary statistics of K2O values. ........................................................................................... 149 Figure 5-5: Summary Fe2O3 statistics. ........................................................................................................ 150 Figure 5-6 Summary statistics of MnO. ..................................................................................................... 151 Figure 5-7 Summary statistics of CaO. ....................................................................................................... 153 Figure 5-8 Summary statistics of MgO. ..................................................................................................... 153 Figure 5-9: Figure indicating the probability plot of CaO log concentrations indicating bimodal distribution of three populations which is represented by 78 and 22% respectively. Population 1 indicates the mean of 0.203 (- 0.075 and +0.551 std.-dev), population 2 indicate the mean of 3.029 (-1.433 and +6.401 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 0.028 wt.% and maximum of 1.496 wt. %, population 2 minimum of 0.678 wt.% and maximum of 13.526 wt.%. ........................................................................... 155 Figure 5-10: Figure indicating the uni-element distribution of CaO on the ROC, the red is higher than the threshold value. .......................................................................................................................................................... 156 Figure 5-11: Figure indicating the probability plot of sodium log concentrations indicating bimodal distribution of three populations which is represented by 20, 70 and 10% respectively. Population 1 indicates the mean of 0.013 (-0.009 and +0.021 std.-dev), population 2 indicate the mean of 0.136 (-0.064 and +0.290 std.-dev) and population 3 indicate the mean of 1.136 (-0.762 and +1.694). The thresholds calculated at 2 std.-dev for population 1 is minimum 0.005 wt.% and maximum of 0.033 wt.%, population 2 minimum of 0.030 wt.% and maximum of 0.619 wt.% and population 3 minimum of 0.511 wt.% and the maximum of 2.526 wt.%. ........................ 157 Figure 5-12: Figure indicating the uni-element distribution of sodium on the ROC, the red are higher than the threshold value............................................................................................................................................ 158 Figure 5-13: Figure indicating the probability plot of magnesium log concentrations indicating bimodal distribution of three populations which is represented by 75 and 25% respectively. Population 1 indicates the mean of 0.113 (-0.036 and +0.353 std.-dev), population 2 indicate the mean of 0.052 (-0.322 and +12.564 std.- dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 0.012 wt.% and maximum of 1.100 wt.%, population 2 minimum of 0.052 wt.% and maximum of 78.453 wt.%. ........................................... 159 xi | P a g e Figure 5-14: Figure indicating the uni-element distribution of magnesium on the ROC. .......................... 160 Figure 5-15: Figure indicating the probability plot of chromium log concentrations indicating bimodal distribution of two populations, which is represented by 15 and 85% respectively. Population 1 indicates the mean of 6.447 (-2.484 and +16.730 std.-dev), population 2 indicate the mean of 173.093 (-83.683 and +358.032 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 0.957 ppm and maximum of 43.415 ppm, population 2 minimum of 40.457 ppm and maximum of 740.569 ppm. .................................................... 161 Figure 5-16: Figure indicating the uni-element distribution of chromium (ppm) on the ROC, the red are above the threshold value............................................................................................................................................ 162 Figure 5-17: Figure indicating the probability plot of aluminium log concentrations indicating bimodal distribution of two populations which is represented by 30 and 70% respectively. Population 1 indicates the mean of 2.990 (-1.995 and +4.479 std.-dev), population 2 indicate the mean of 8.401 (-6.011 and +11.740 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 1.332 wt.% and maximum of 6.711 wt.%, population 2 minimum of 4.301 wt.% and maximum of 16.407 wt.%. ...................................................... 163 Figure 5-18: Figure indicating the uni-element distribution of aluminium on the ROC, the red are above thethreshold value. ...................................................................................................................................... 164 Figure 5-19: Figure indicating the probability plot of silica log concentrations indicating bimodal distribution of two populations which is represented by 5 and 95% respectively. Population 1 indicates the mean of 35.385 (- 25.227 and +49.534 std.-dev), population 2 indicate the mean of 76.372 (-64.934 and +89.825 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 18.057 ppm and maximum of 69.341 ppm, population 2 minimum of 55.208 ppm and maximum of 105.649 ppm. .................................................... 165 Figure 5-20: Figure indicating the uni-element distribution of As on the ROC, the red are above thethreshold value. .......................................................................................................................................................... 166 Figure 5-21: Figure indicating the probability plot of potassium log concentrations indicating bimodal distribution of two populations which is represented by 15 and 85% respectively. Population 1 indicates the mean of 0.216 (- 0.130 and +0.359 std.-dev), population 2 indicate the mean of 1.062 (-0.659 and +1.710 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 0.078 wt.% and maximum of 0.598 wt.%, population 2 minimum of 0.409 wt.% and maximum of 2.753 wt.%. ............................................................................. 167 Figure 5-22: Figure indicating the uni-element distribution of potassium on the ROC, the red are above the threshold values. ......................................................................................................................................... 168 Figure 5-23: Figure indicating the probability plot of phosphate log concentrations indicating bimodal distribution of two populations which is represented by 95 and 5% respectively. Population 1 indicates the mean of 0.070 (- 0.036 and +0.138 std.-dev), population 2 indicate the mean of 0.403 (-0.228 and +0.712 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 0.018 wt.% and maximum of 0.269 wt.%, population 2 minimum of 0.129 wt.% and maximum of 1.256 wt.%. ............................................................................. 169 Figure 5-24: Figure indicating the uni-element distribution of phosphorus on the ROC. .......................... 170 Figure 5-25: Figure indicating the probability plot of iron log concentrations indicating bimodal distribution of three populations which is represented by 38, 57 and 5% respectively. Population 1 indicates the mean of 1.942 xii | P a g e (-1.280 and +2.945 std.-dev), population 2 indicate the mean of 6.517 (-4.632 and +9.169 std.-dev) and population 3 indicate the mean of 18.846 (-13.830 and +25.680). The thresholds calculated at 2 std.-dev for population 1 is minimum 0.844 wt.% and maximum of 4.467 wt.%, population 2 minimum of 3.293 wt.% and maximum of 12.900 wt.% and population 3 minimum of 10.150 wt.% and the maximum of 34.993 wt.%. .................. 171 Figure 5-26: Figure indicating the uni-element distribution of total iron on the ROC, the red symbol is above the threshold. .................................................................................................................................................... 172 Figure 5-27: Figure indicating the probability plot of As log concentrations indicating bimodal distribution of three populations divided at 80% and 90% percentile, population 1 indicate the mean of 4.963 (-3.1 and +7.946 std.-dev), population 2 indicate the mean of 225.685 (-100.215 and +470.337 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 1.936 ppm and maximum of 12.721 ppm, population 2 minimum of 51.907 ppm and maximum of 908.552 ppm. .............................................................................................. 177 Figure 5-28: The normal probability plot, histogram and box and whisker plots with the summary statistics of As in the ROC. The inflexion points are the borders between different populations ....................................... 178 Figure 5-29: Figure indicating the uni-element distribution of As on the ROC. The anomalous distribution of As is mainly located north-east of Witbank and SSW of Middelburg area. .................................................... 179 Figure 5-30: Figure indicating the probability plot of indicating bimodal distribution of three populations of U at 78, 20 and 2%. Population 1 indicates the mean of 2.437 (-1.829 and +3.247 std.-dev), population 2 indicate the mean of 63.725 (-31.250 and +129.947 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 1.372 ppm and maximum of 4.327 ppm, population 2 minimum of 15.325 ppm and maximum of 264.989 ppm and population 3 minimum of 143.829 ppm and the maximum of 1898 ppm. ..................... 181 Figure 5-31: Depicts the normal probability plot, the histogram, and the box and whisker plots for U in the ROC. .................................................................................................................................................................... 182 Figure 5-32: Figure indicating the element distribution of U on the ROC. ................................................ 183 Figure 5-33: Figure indicating the probability plot of indicating bimodal distribution of two populations of Zn divided at 60% percentile, population 1 indicate the mean of 25.140 (-11.872 and +53.235 std.-dev), population 2 indicate the mean of 183.987 (-94.790 and +356.808 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is minimum 5.607 ppm and maximum of 112.728 ppm, population 2 minimum of 48.857 ppm and maximum of 692.261 ppm.......................................................................................................................... 187 Figure 5-34: The normal probability plot, histogram and box and whisker plots with the summary statistics of Zn in the ROC. ................................................................................................................................................. 188 Figure 5-35: Figure indicating the uni-element distribution of Zinc on the ROC. The anomalous distribution of Zn is mainly located north-east of Witbank and SSW of Middelburg area, the samples the downstream deportment of metals. .................................................................................................................................................... 189 Figure 5-36: Figure indicating the probability plot of indicating bimodal distribution of three populations of Pb at 9, 86 and 5%. Population 1 indicates the mean of 5.864 (-4.161 and +8.265 std.-dev), population 2 indicate the mean of 20.698 (-13.175 and +32.516 std.-dev). The thresholds calculated at 2 std.-dev for population 1 is xiii | P a g e minimum 2.952 ppm and maximum of 11.648 ppm, population 2 minimum of 8.387 ppm and maximum of 51.080 ppm and population 3 minimum of 44.671 ppm and the maximum of 117.154 ppm. ............................... 191 Figure 5-37: The normal probability plot, histogram and box and whisker plots with the summary statistics of Pb in the ROC. ................................................................................................................................................. 192 Figure 5-38: Figure indicating the uni-element distribution of Pb on the ROC. ........................................ 193 Figure 5-39: Figure indicating the probability plot of V indicating bimodal distribution of three populations which is represented by 30, 68 and 2% respectively. Population 1 indicates the mean of 5.460 (-2.072 and +14.391 std.- dev), population 2 indicate the mean of 100.877 (-62.906 and +161.761 std.-dev) and population 3 indicate the mean of 406.550 (-262.818 and +628.885). The thresholds calculated at 2 std.-dev for population 1 is minimum 0.786 and maximum of 37.928, population 2 minimum of 39.231 and maximum of 259.392 and population 3 minimum of 169.902 and the maximum of 972.812. ................................................................................. 195 Figure 5-40: Figure indicating the uni-element distribution of V on the ROC. .......................................... 196 Figure 5-41: Illustrations of the processes of fate and transport of metals (after Caruso et al., 2008). ...... 197 Figure 5-42: Sediment geochemical trace element data normalized to the upper continental crust (Taylor and McLennon, 1985), for the enrichment of the trace metals. ......................................................................... 201 Figure 5-43: Sediment geochemical trace element data normalized to the upper crust (Taylor and McLennon, 1985), for the enrichment of the trace metals. ............................................................................................ 201 Figure 5-44: Sediment geochemical trace element data normalized to the average rrust (Weaver and Tarney, 1984), for the enrichment of the trace metals. ............................................................................................ 202 Figure 5-45: Metal association using the correspondence analysis, displaying different axes directions for various trace elements roughly showing different fractionation/mobilization behaviour; the black dots are the sample points. ......................................................................................................................................................... 202 Figure 5-46: Sediment geochemical trace element data normalized to the upper continental crust (Taylor and McLennon, 1985), for the enrichment of the trace metals on samples located in 1: dykes and sills; 2: granite (granophyre, felsites and rhyolites); 3: mudstones, sandstones and diamictite; 4: Vryheid (sandstones, shale and coal). ........................................................................................................................................................... 203 Figure 5-47 A weighted sum map (ppm) dustribution of Zn, Pb and As from the stream sediment. ...... 203 xiv | P a g e LIST OF TABLES Table 2-1: Classification of the Karoo Supergroup's lithostratigraphy (after Azzie, 2002).......................... 17 Table 3-1: Presents the LLD and the XRF standards in CGS for some majors and largely trace elements. 31 Table 3-2: The lower LLD and the standards used by XRF in CGS for the major oxide. ............................ 32 Table 3-3: The results (wt.%) of X-ray diffraction analyses of coal seams with the footwall and the extends above (ZFN1512 and 1510) .................................................................................................................................... 34 Table 3-4: The colour map Pearson correlation matrix of major in wt.% and traces in ppm for the Witbank coalfield geologial units in ZFN 1510, significant at p < .05, classifications after Moore et al. (2013). ..... 47 Table 3-5: The colour map Pearson correlation matrix of major in wt.% and traces in ppm for the Witbank coalfield geologial units in ZFN1512, significant at p < .05, classifications after Moore et al. (2013). ...... 48 Table 3-6: Trace elements associated with minerals in Australian and South African coals (after Dale, 1999, 2003; Swaine, 1990; Palmer 1985; and present study). .......................................................................................... 68 Table 4-1: Provides parameters for ABA screening (after Price et al., 1997b). ........................................... 71 Table 4-2: The ABA findings for samples from borehole ZFN1510, along with their interpretation. ......... 77 Table 4-3: The table indicating the 27 samples for the kinetic test. ............................................................. 82 Table 4-4: Saturation indices (SI) results for mineral prediction for coal seams using GWB. ................... 106 Table 4-5: Saturation indices (SI) results for mineral prediction for above and below units of coal seams using GWB. .......................................................................................................................................................... 107 Table 4-6: Composite leachate cumulative for lithological units input data for kinetic reactive model, A-B are units above and below coal seams. ............................................................................................................. 114 Table 5-1: Summary data for the major elements (wt%) and trace metals in stream sediments (ppm). ..... 145 Table 5-2: Colour map of Pearson correlations matrix for the 246 stream sediments trace element data, the correlations are significant at p < .05, classifications after Moore et al. (2013). ........................................ 175 Table 5-3: Color map of Pearson correlations matrix for the 246 stream sediments major oxide data, the correlations are significant at p < .05, classifications after Moore et al. (2013). ........................................ 176 Table 6-1: Descriptive data (minimum, maximum, mean, std.-dev, and median) of major (wt. %) and trace (ppm) elements in the bedrock and stream sediments of the Witbank coalfield. .................................................. 212 Table 6-2: Loading of elements of the source rocks compared to the stream sediment data. ..................... 213 Table 6-3: Metal comparison to the world sediment quality guidelines of the ROC stream sediments averages. .................................................................................................................................................................... 214 xv | P a g e GLOSSARY Acid Base Accounting (ABA) Acid potential (AP) Acid Rock Drainage (ARD) American Society for Testing and Materials (ASTM) Circumneutral mine waters (CMW) Council for Geoscience (CGS) Crossed polar (XPL) Department of Forestry, Fisheries and the Environment (DFFE) Department of Minerals Resources and Energy (DMRE) Department of Water Affairs and Forestry (DWAF) Energy-dispersive X-ray spectroscopy (EDS) Enrichment factor (EF) Environmental Impact Assessment (EIA) Environmental Management Plan (EMP) Environmental Protection Agency (US EPA) Geochemist’s Workbench (GWB) Humidity Cell Leach (HCL) Institute for Groundwater Studies (IGS) Loss of Ignition (LOI) Masters of Science (MSc) Mine Drainage (MD) Mine Environment Neutral Drainage (MEND) Mineral and Petroleum Resources Development Act (MPRDA) National Environment Management Act (NEMA) National Environmental Policy Act (NEPA) Net neutralization potential (NNP) Net potential ratio (NPR) Neutralization potential (NP) Olifants Primary catchment (OPC) Plane polarised light (PPL) Riet-Olifants catchment (ROC) Simultaneous X-ray Fluorescence Spectrometer (SXRF) South African Mineral Database (SAMINDABA) Standard deviation (std.-dev.) Sediment Quality Guidelines (SQG) The Lower Limit of Detection (LLD) University of the Free State (UFS) X-Ray Diffraction (XRD) X-ray Fluorescence Spectrometer (XRF) xvi | P a g e CONTENTS DECLARATION ................................................................................................................... i PREFACE ........................................................................................................................... i ACKNOWLEDGEMENT ...................................................................................................... ii EXECUTIVE SUMMARY .................................................................................................... iv LIST OF FIGURES ............................................................................................................. vii LIST OF TABLES ............................................................................................................... xiv GLOSSARY ....................................................................................................................... xv 1 INTRODUCTION ....................................................................................................... 1 1.1 RESEARCH MOTIVATION ................................................................................................1 1.2 THE STUDY AREA............................................................................................................3 1.3 RESEARCH BACKGROUND ...............................................................................................7 1.4 RESEARCH OBJECTIVES ...................................................................................................9 1.5 CONCEPTUAL MODEL .....................................................................................................9 1.6 HYPOTHESIS ................................................................................................................. 10 2 GEOLOGICAL SETTING OF THE ROC ........................................................................ 13 2.1 PRE-KAROO GEOLOGY .................................................................................................. 13 2.2 WITBANK COALFIELD ................................................................................................... 21 3 PETROGRAPHY AND GEOCHEMISTRY OF THE SOURCE ROCK UNITS ........................ 27 3.1 INTRODUCTION ........................................................................................................... 27 3.2 METHODOLOGY ........................................................................................................... 27 3.2.1 Borehole core samples description .......................................................................................... 28 3.2.2 Analytical Procedure ................................................................................................................. 29 3.2.2.1 X-ray diffraction (XRD)......................................................................................................... 29 3.2.2.2 X-ray fluorescence spectrometry (XRF) ............................................................................... 30 3.3 RESULTS ...................................................................................................................... 32 3.3.1 Mineralogy of stratigraphic units.............................................................................................. 32 3.3.1.1 Inorganic geological unit ..................................................................................................... 33 3.3.1.2 Organic geological unit ........................................................................................................ 36 3.3.1.2.1 Coal Seam No. 5 ....................................................................................................... 36 3.3.1.2.2 Coal Seam No. 4 ....................................................................................................... 36 3.3.1.2.3 Coal Seam No. 3 ....................................................................................................... 37 3.3.1.2.4 Coal Seam No. 2 ....................................................................................................... 37 3.3.2 Geological units petrology ........................................................................................................ 38 3.3.2.1 Above Coal Seam no. 5 ........................................................................................................ 38 xvii | P a g e 3.3.2.2 Coal Seam No. 5 .................................................................................................................. 41 3.3.2.3 Within No. 5 and No. 4 Coal Seam ...................................................................................... 41 3.3.2.4 Coal Seam No. 4 .................................................................................................................. 42 3.3.2.5 Within coal seam No.4 and No.3 ......................................................................................... 43 3.3.2.6 Coal Seam No. 3 .................................................................................................................. 44 3.3.2.7 Coal Seam No. 2 .................................................................................................................. 44 3.3.2.8 Basement rocks ................................................................................................................... 45 3.3.3 Geochemical elements distribution .......................................................................................... 46 3.4 DISCUSSIONS AND CONCLUSSION ................................................................................ 55 3.4.1 Mineralogical profile distribution ............................................................................................. 55 3.4.2 Major elements distribution ..................................................................................................... 61 3.4.3 Trace elements distribution ...................................................................................................... 62 3.5 SUMMARY OUTCOMES ................................................................................................ 67 4 MINE DRAINAGE: CASE STUDY GEODEHOOP COLLIERY ........................................... 69 4.1 INTRODUCTION ........................................................................................................... 69 4.2 ACID BASE ACCOUNTING (ABA) .................................................................................... 70 4.2.1 Screening criteria ...................................................................................................................... 71 4.2.2 Results....................................................................................................................................... 71 4.2.2.1 Coal seams .......................................................................................................................... 72 4.2.2.2 Other geological units ......................................................................................................... 73 4.3 HUMIDITY CELL LEACH TESTS ........................................................................................ 81 4.3.1 Background ............................................................................................................................... 81 4.3.2 Methodology ............................................................................................................................ 81 4.3.2.1 Sampling .............................................................................................................................. 81 4.3.2.2 Humidity cell (IGS) ............................................................................................................... 82 4.3.3 Results....................................................................................................................................... 84 4.3.3.1 Leachate quality .................................................................................................................. 84 4.3.3.2 Acid production lithological units ....................................................................................... 89 4.3.3.2.1 Coal seam number 5 ................................................................................................ 89 4.3.3.2.2 Rock units between C5 and C4 (Sandstone) ............................................................ 89 4.3.3.2.3 Coal seam number 4 ................................................................................................ 93 4.3.3.3 Non-acid generation lithological units ................................................................................ 98 4.3.3.3.1 Rock units above C5 (Sandstone /siltstone, Dolerite) .............................................. 98 4.4 DISCUSSION AND CONCLUSIONS ................................................................................ 102 4.4.1 General observation ............................................................................................................... 102 4.4.2 Saturation index of metals ...................................................................................................... 103 4.4.3 Kinetic models ........................................................................................................................ 110 4.4.3.1 Coal seams ........................................................................................................................ 110 4.4.3.2 Profile above/below coal seams ....................................................................................... 119 4.4.3.3 Reaction processes ............................................................................................................ 123 4.4.3.3.1 Sulphide-oxidation ................................................................................................. 123 4.4.3.3.2 Acid neutralization and alkalinity generation (carbonation) ................................. 123 4.4.3.3.3 Ion exchange or adsorption ................................................................................... 124 4.5 Summary conclusion .................................................................................................. 129 5 STREAM SEDIMENTS GEOCHEMISTRY .................................................................. 132 5.1 INTRODUCTION ......................................................................................................... 132 xviii | P a g e 5.2 SAMPLING AND METHODOLOGY ................................................................................ 134 5.2.1 Sampling and Preparations ..................................................................................................... 134 5.2.2 Fluorescence X-Ray Spectrometer (XRF) ................................................................................ 137 5.2.3 Limit of Detection ................................................................................................................... 137 5.2.4 Calculating the Enrichment Factor ......................................................................................... 139 5.3 RESULTS ANALYSIS ..................................................................................................... 144 5.3.1 Major Oxides ........................................................................................................................... 144 5.3.2 Trace elements ....................................................................................................................... 173 5.3.2.1 Arsenic ............................................................................................................................... 173 5.3.2.2 Uranium ............................................................................................................................ 180 5.3.2.3 Zinc .................................................................................................................................... 184 5.3.2.4 Lead ................................................................................................................................... 190 5.3.2.5 Vanadium .......................................................................................................................... 194 5.4 DISCUSSION AND CONCLUSIONS ................................................................................ 197 5.4.1 Major oxides ........................................................................................................................... 198 5.4.2 Trace elements ....................................................................................................................... 199 6 SUMMARY AND RECOMMENDATIONS ................................................................. 207 6.1 DISCUSSION AND INTEGRATION FINDINGS ................................................................. 207 6.2 CONCLUSION REMARKS ............................................................................................. 210 7 WASTE MANAGEMENT FRAMEWORK GUIDELINE PROPOSAL ............................... 218 8 REFERENCES ........................................................................................................ 220 APPENDIX A: COAL PETROGRAPHY ............................................................................... 249 APPENDIX B: X-RAY DIFFRACTION (XRD) RESULTS ......................................................... 273 APPENDIX C: MAJOR AND TRACE ELEMENTS SCATTERPLOTS ......................................... 280 APPENDIX D: X-RAY FLUORESCENCE SPECTROMETRY (XRF) MAJOR (wt.%) AND TRACES (PPM) .......................................................................................................................... 293 APPENDIX E: KINETIC TEST RESULTS CORRELATIONS MATRIX BH1-27 ............................ 297 APPENDIX F: KINETIC TEST GRAPHICAL SUMMARY ....................................................... 324 APPENDIX G: HUMIDITY CELL LEACH TEST FOR 31 WEEKS RESULTS ............................... 336 APPENDIX H: BOREHOLE LOG ZFN 1510 AND 1512 ....................................................... 355 APPENDIX I: LITHOLOGICAL MAJOR AND TRACES AVERAGES OF BHZFN1510 AND ZFN1512 .................................................................................................................................... 360 APPENDIX J: ROC STREAM SEDIMENT GEOCHEMICAL MAJOR (wt.%) AND TRACES (PPM) XRF DATA .................................................................................................................... 370 APPENDIX K: CUMMULATIVE INITIAL AND FINAL (mg/L) ............................................... 376 APPENDIX L: OTHER KINETIC MODEL PLOTS .................................................................. 378 APPENDIX M: CUMULATIVE MASS INFLUXES AND EFFLUXES OVER SIMULATION ........... 397 0 | P a g e 1 | P a g e 1 INTRODUCTION The introduction part covers the motivation of the research, the introduction to the study area, research background, geological context, and a summary of prior work through a literature search. 1.1 RESEARCH MOTIVATION Transport of metals from the source to the receiving environment in active and remediated mines may be done by elucidating the mobilization processes involved and predicting mine drainage (MD), which plays a role in the area of investigation, in this example, the Riet- Olifants catchment (ROC). As per the Mineral and Petroleum Resources Development Act (MPRDA) of 2008, the prediction of MD is not required for the development or exploitation of a mineral deposit in South Africa. The management requirements for environmental impacts are stipulated in the National Environment Management Act (NEMA) of 1998. However section 36 of the MPRDA Act of 2008, the minister of Department of Mineral Resources and Energy (DMRE), in consultation with the minister of Department of Forestry, Fisheries and the Environment (DFFE) may intervene when there is identified impact during prospecting, mining, reconnaissance, exploration or production operations or activities incidental thereto cause or results in ecological degradation. According to section 24 (1) of the NEMA Act of 1998, mining licenses in South Africa must be issued prior to the submission of an MD report, which includes detailing all potential consequences and the management thereof. However, MD assessment is not explicitly defined as a method or technique for identifying the environmental consequences caused by the extraction of mineral resources. In "developed nations" such as Canada, it is doubtful that a mining licence would be issued if the MD issues are not adequately handled (MEND, 1995; 1996). Notably, the latter criterion was also a requirement of the Environmental Impact Assessment (EIA) law of the National Environmental Policy Act (NEPA) in the United States at the end of 1969. 2 | P a g e In succeeding years, this trend continued (https://www.westerncape.gov.za/eadp/files/atoms/files/EIA 2015.pdf):  Administrative steps by Japan in 1972 (EIA guidelines only; law not enacted until 1997), Canada in 1973 (Federal Directive), and New Zealand in 1974 (Cabinet Minute).  Legislation: 1974 for Australia, 1974 for Colombia, 1975 for West Germany, and 1991 for all of Germany More than a hundred countries assess mine drainage (MD) as part of their Environmental Impact Assessment (EIA) or Environmental Management Plan (EMP) procedures, in terms of mining law (MEND, 1995; 1996). Environmentally competent waste rock management plans are necessary to effectively, economically, and efficiently estimate the quality of drainage generated by the lithologies or rock units mined to reach the ore and the possibility for future unfavorable effects (MEND, 1995). As prevention is preferable to treatment, failure to apply this method has shown to cost governments billions of rands to remedy the environmental effects created. In South Africa, the issues associated with MD are enormous. Many gold mines in the Witwatersrand Basin and the coalfields, for instance, are abandoned and ownerless, with or without monitoring or water treatment. These mines constantly contribute metals and acidity to the receiving environment or waterways. Environmental worries have been expressed for the future of mining in the Witbank coalfield, which greatly contributes to the country's economic growth (McCarthy and Pretorius, 2009). The abandoned mines are flooded, and metals are transported through seeping into the receptor zone as sediments and water are enriched (Netshitungulwana et al., 2013). This research focuses mostly on the ROC, which is dominated by rocks of the Karoo Supergroup, with the Witbank coalfield serving as key coal resource in the investigation area. Similar initiatives have been a subject of preliminary research in the Witbank coalfield. Recent research by Pinetown and Boer (2006) focuses more on the quantitative evaluation of minerals in coal and the possibility for acid production, but does not dispute the quantity and mobility https://www.westerncape.gov.za/eadp/files/atoms/files/EIA%202015.pdf 3 | P a g e of the metals connected with the geological units of the Witbank coalfield and the receptor. This study is new in that it examines the fate of metal transport from its origins to its receiving environment. This thesis discusses the geochemical characterisation of the Witbank coalfield geological strata and the geochemistry of stream sediments representing the receiving environment. The results of this study should inspire future mining in South Africa to integrate a prediction of the future environmental effect associated with element mobility from geological units that would be encountered during the value chain of mineral exploitation. As severe pollution has detrimental effects on socio-economic progress and the ecology, the findings of this study can also serve as a guide for the government entities in amending the applicable laws of MPRDA and NEMA so that South Africa can become one of the countries with little or no pollution. 1.2 THE STUDY AREA The Witbank coalfield is situated in the ROC, a sub catchment in the upper reaches of the Olifants primary catchment (OPC). The Witbank coalfield is located on the western side of Mpumalanga Province, which consists of the towns of Witbank, Middleburg, Kriel, Hendrina, Bethal, and Arnot (Figure 1-1). The Little Olifants-Riet sub-catchments include the area drained by the upper sections of the Olifants, Little Olifants, and Riet rivers and its tributaries, down to where the Olifants River joins the Wilge River at the Loskop dam (Ashton et al., 2001). The sub-catchment receives additional water from the Vaal and Crocodile/Komati catchments through three inter-basin transfer projects (Ashton et al., 2001). All rivers or streams within this sub-catchment are perennial, and each river or stream has several tiny wetlands (Ashton et al., 2001; Marneweck et al., 2001). Currently, the Witbank coalfield is the most important producing coalfield in the country. The coalfied extend 180 kilometers from Brakpan to the Springs region in the west, to Belfast in the east, and roughly 40 kilometers north to south. The watershed sits inside the Karoo basin's Witbank and Highveld coalfields. These coalfields generate 48% of the nation's total electrical generating capacity (Hobbs et al., 2008). With over 55 collieries, the Witbank coalfield is the most significant center of South 4 | P a g e Africa's contemporary coal mining activities (Banks et al., 2011). In the Mpumalanga Province of South Africa, near Witbank and (to the northeast) Middelburg are several coal-related and other resources. Figure 1-1: A map of the research region, the ROC, Mpumalanga Province highlighted in blue. According to the most recent study by the DMRE, more than 75% of South Africa's residual coal deposits are located in the Highveld and Witbank coalfields. Nonetheless, these resources will be depleted within the next century (Ratshomo and Nembahe, 2016). Historically, the Witbank coalfield's No. 2 seam was the primary objective for mining. However, its reserves have diminished dramatically over the past two decades, causing the No. 4 Seam to become the principal export source (Figure 1-2). The seam No. 4 in situ coal is reported to have more ash and inertinite than, for instance, the No. 2 seam in situ coal (Pinetown and Boer, 2006). 5 | P a g e Industrial and agricultural land usage in the region is diverse and extensive. The Highveld Steel and vanadium processing factory located west of Witbank and the stainless steel mill in Middelburg are the most noteworthy (Banks et al., 2011). Several Eskom power plants, including Kendal, Matla, Kriel, Duvha, Arnot, Hendrina, and Komati, get coal from nearby mines. Energy content is a major factor in determining the price of coal (Banks et al., 2011). The majority of the converted natural land is under agriculture, including commercial plantations, and maize is the primary crop produced in the catchment region. Some sections are used for mixed agricultural, including cattle, dairy, poultry, corn, and potatoes (Banks et al., 2011). 6 | P a g e Figure 1-2: A map showing a location for the OPC area, South Africa. 7 | P a g e 1.3 RESEARCH BACKGROUND The ROC is part of the OPC area, which includes nine sub-catchments labeled B1 through B9 and stretches over the South African and Mozambican borders (Ashton et al., 2001; Netshitungulwana et al., 2015; Netshitungulwana and Yibas, 2012). It has an approximate overall size of 87,000 km2. The ROC is designated as a B1 catchment, where the majority of mining activity are concentrated around the cities of Witbank (Emalahleni) and Middleburg, which in turn straddles the provinces of Mpumalanga and Limpopo (Netshitungulwana et al., 2015). In South Africa, the OPC region is home to extensive mining operations for a variety of minerals, including coal, gold, and base metals. It is comprised of nine subcatchments (Figure 1-2). In recent years, the watershed has been scrutinized for its high degree of metal pollution. Although industrial and agricultural activities are also significant, the contribution of contamination to the OPC from mining activities within the catchment is significant as a result of intense coal, gold, and base metals mining and from ferrochrome and Vanadium processing plants located in Emalahleni and Middleburg towns within the catchment area (Figure 1-2) and has not yet been fully quantified (Netshitungulwana and Yibas, 2012). Recently, the OPC have been the subject of intense public criticism. Despite clear indications that the Olifants river's water quality has been decreasing due to industrial, mining, and agricultural operations, the cause of periodic fish and crocodile mortality in the river system remains unknown (de Villiers and Mkwelo, 2009; Yibas et al., 2013; Netshitungulwana and Yibas, 2012). The effects are visible in the Witbank region, where there are several operational, abandoned, and ownerless coal mines. The asbestos mining areas (not active) of the Penge and other areas in Mpumalanga, the heavy mineral sand operations (not active), and areas of extensive smaller-scale mining such as the Barberton and Giyani greenstone belts and the Pilgrim's Rest Goldfield as potential pollution contributors all drain into the OPC (Netshitungulwana and Yibas, 2012). Using a catchment-by-catchment methodology, the Council for Geoscience (CGS) and the DMRE initiated a research in 2012 to examine the severity of the mining impacts on the 8 | P a g e country's water resources and ecology (Yibas et al., 2013). The OPC area has been prioritized for study because of the high concentration of mining activities within its territory (Yibas et al., 2013). Although contamination has been investigated, little or no effort has been made to comprehend the fate of metal transport from sources to the receiving environment. Understanding the geological and geochemical processes of the various geological units can aid in better managing the element load discharged by present and future mining. As implemented by the United States Environmental Protection Agency (US EPA), the outcome of this reseach can benefit the government in formulating coal mining effluent guidelines and regulations. For a little to no-contamination strategy, it is necessary to characterize in the new coal-mining areas. In so-called "intelligent cities," a zero-waste / zero-contamination attitude is currently on the rise (https://www.epa.gov/transforming-waste-tool/how-communities- have-defined-zero-waste). In order to reach such aims in coal mining in South Africa, it is essential to comprehend the relevant geological processes as highlighted above. Consequently, this research is the initial step towards reaching such objectives. The processes that lead to contamination are mainly enhanced by weathering processes of the geological materials. Under conditions of element leach through oxidation and weathering, the impact of released metals on the hydrosphere and atmosphere may be minimal. In a mining- related scenario of ground disturbance, leaching and mobility of coalbed-contained elements increase due to exposure to environmental conditions such as air infiltration and oxidation. With the aid of water and air, mine drainage occurs, damaging the receiving environment. The transport medium may be seepage to subsurface water or runoff. https://www.epa.gov/transforming-waste-tool/how-communities-have-defined-zero-waste https://www.epa.gov/transforming-waste-tool/how-communities-have-defined-zero-waste 9 | P a g e 1.4 RESEARCH OBJECTIVES The research focuses on the ROC region, which is situated in the upper parts of the OPC. The primary objective is to identify components in the source rocks and stream sediments of the drainage area that are enriched relative to their naturally occurring source rocks and represent an anthropogenic vs a geogenic input. To fulfill the primary goals, threshold determination of stream sediments and static and kinetic testing for acid base accounting of coalbed core samples will be employed. The specific goals are as follows:  Determine the geochemistry, mineralogy, and petrology of the source rocks by deciphering the lithological units of the drilled core at the Goedehoep Colliery (chapter 3).  To determine the mine drainage capability of the lithological units of the source rock utilizing the drilled core of the Goedehoop coal mine and conducting static tests and 31 weeks of kinetic test leaching experiments (chapter 4).  Determine the element concentrations of the stream sediments and differentiate between background concentrations and anomalies (anthropogenic and geogenic enrichment) using conventional geochemical exploration techniques (chapter 5).  Outline a framework for the management of mine waste deposits in the Emalahleni coalfields of South Africa (chapter 7). 1.5 CONCEPTUAL MODEL To fulfill this study's primary objective, it is necessary to understand the source, pathway, and receptors of elements in the source rocks, stream flows, and sediments of the ROC as shown in Figure 1-3. The paradigm is depicted in Figure 1-4 (after Morin and Hutt, 1999), which investigates the paths of element transport in the context of mine drainage chemistry prediction. For environmental concerns, Morin and Hutt (1999) identify three fundamental aspects that must be addressed for each risk: 10 | P a g e  A pollutant (source) is a substance in, on, or under the lithosphere that has the potential to cause harm or contamination to the surrounding environment.  A pathway is "a conduit for the movement of contaminants, including geological features, hydrogeology, and surface water streams."  The presence of a pollutant affects a receptor. 1.6 HYPOTHESIS The sediment-water interaction mechanisms include dissolution or chemical weathering, element complexation in addition to sediment particle adsorption or precipitation. To appreciate these processes, it is necessary to know the geological and geochemical processes of element leaching of the geological units of the Witbank coalfield. The stratigraphic sequence in the Witbank coalfield show uniformity in the cross section, and is syngenetic. In this study it is represented by the stratigraphic core from the Goedehoop region. This may be accomplished by determining the element concentrations in sediments in the receiving environment. The Witbank coalfield is composed of five coal seams (seams 1 through 5), which were formed under oxidizing conditions and are distinguished by the presence of inertinite, vitrite, and sulphide minerals. The hanging and footwall units comprise sandstones and shales composed of sulphide minerals. S, As, and F elements from coal and subsequent stratigraphic units may be leached and concentrate in effluent and receptor. Under favorable environmental conditions (oxidation or reduction), mobile elements can be complexed, transported, and subsequently precipitated or adsorbed by clay or fine sediments. Two significant aquifers, the upper and lower Ecca aquifers, interact continuously with the stratigraphic strata. The water dissolves, complex, and transports elements to recharge neighboring streams and bodies of water. The processes of desorption/dissolution and precipitation/adsoption are particularly applicable to the coal waste rock dumps and tailing facilities in the catchment area. In order to characterize the aforementioned process and enable the prediction of mine drainage, this thesis will focus on the assessment, development, and implementation (Figure 1-3) of static and kinetic leaching studies of coal beds and related rocks as well as on stream sediment composition. 11 | P a g e Figure 1-3: Simplified conceptual model highlighting the sources pathways and receptor environment for the metals. Rain water infiltration on exposed geological material (e.g., mine residue deposit Chemical Reaction: oxidation-reduction, ion exchange, precipitation and carbonation Underground water contamination Surface seepage, runoff and underground seepage River channel: mixing, adsorption and precipitation Other sources: agricultural, seewages, power plants etc. Recreational activities 12 | P a g e Figure 1-4: The mine drainage chemical prediction wheel (adapted from Morin and Hutt, 1999). 13 | P a g e 2 GEOLOGICAL SETTING OF THE ROC As indicated in Figure 2-1, the Vryheid Formation of the Ecca Group, Karoo Supergroup is the predominant geology in the ROC. These rocks sit on pre-Karoo basement rocks. The dolomite rocks of the Transvaal Supergroup are exposed south of Delmas. In the core region of Emalahleni, the exposed Bushveld felsites and granites on the eastern side of Emalahleni town, as well as the Transvaal sedimentary rocks, are visible. 2.1 PRE-KAROO GEOLOGY The Pretoria Group (2.4 to 2.1 Ga) contains the ROC's oldest shale and quartzite rocks (2.4 to 2.1 Ga) (Martini, 1998; Eriksson et al., 1995). The Rooiberg Group overlies the Pretoria Group, possibly disconformably (Cheney and Twist, 1991) and is composed of volcanics with a slight sedimentary disconformity composed of shale and greywacke (Twist and French, 1983; Twist, 1985; Harmer and Farrow, 1995; Schweitzer et al., 1995; Hatton and Schweitzer, 1995). In the eastern portion of the Cullinan-Witbank basin, the Rooiberg Group conformably grades into the Loskop Formation, which consists of 1100 m of red shale intercalated with conglomerate in the lower portion and mostly impure quartzite in the top portion (Clubley-Armstrong, 1977). The Loskop Formation series was considered to be part of the Rooiberg Group. It was deposited in a continental environment (Eriksson et al., 1995). It consists of minor lava flows and granophyre intrusions across the stratigraphic Formation. Similar to the Loskop Formation, the earliest portion of the Waterberg Group consists of red beds. 14 | P a g e Figure 2-1: The regional geological map of the ROC. 15 | P a g e The Loskop Formation is dated between 2.0 and 1.7 Ga and is unconformable with all earlier stratigraphic levels (Jansen, 1982; Cheney and Twist, 1986; Cheney and Twist, 1991). The Bushveld Complex is also present in this research, as seen in Figure 2-1. In this research, the Bushveld Complex is represented by two major lithological units: ultramafic to mafic rocks of the Rustenburg Layered Suite and granophyric to felsic volcanic rocks of the Bushveld granites to granophyres and Rooiberg felsites. The Witbank coalfield in South Africa's Mpumalanga Province is situated in the northern portion of the major Karoo Basin, which was invaded by dolerite dykes and sills during the early stage of Gondwana breakup (Du Plessis, 2008). The Karoo basin's layers are predominantly composed of sandstone, carbonaceous shale, siltstone, minor conglomerate, and many coal seams (Cairncross, 2001; Schmidt, 2006). Figure 2-2 and Table 2-1 demonstrate stratigraphic columns for several regions of the coalfield. This diverse array of sedimentary and structural environments, in which coal seams were formed, has a variety of ages (see Table 2-1). The Palaeoproterozoic (2.06 Ga) Rooiberg Group is characterized by exceptionally high-grade lavas and ignimbrites (Buchanan and Reimold, 1998; Lenhardt et al., 2017). It forms the basis of the strata of the Witbank coalfield. The regional stratigraphy is also established based on geochemistry (chemostratigraphy) as follows; the volcanic rocks of Rooiberg have been split into base rhyolite, high-Ti basalt, low-Ti basaltic andesite, high-Fe-Ti-P andesite, high-Mg and low-Mg felsite, and high-Fe-Ti-P andesite (Schweitzer et al., 1995; Hatton and Schweitzer, 1995). 16 | P a g e Figure 2-2: Generalized stratigraphic columns of the Witbank coalfield (after Smith and Whittaker, 1986). 17 | P a g e Table 2-1: Classification of the Karoo Supergroup's lithostratigraphy (after Azzie, 2002). Supergroup Age (Ma) Group Formation Karoo 140 Jurassic and Upper Triassic Drakensberg Drakensberg 195 Clarens 225 Triassic Elliot 230 Upper Permian and lower Triassic Beaufort Burgersdop Katberg Balfour Koonap & Middleton 260 Middle Permian Upper Ecca Volksrust Middle Ecca Vryheid Lower Ecca Pietmaritzburg 300 Late Carboniferous Dwyka According to Hatton and Schweitzer (1995), "petrographic examinations of these rocks show that the majority of Dullstroom Formation units are metavolcanics and consist of fine-grained groundmass with filled amygdales and phenocrysts. Common constituents of the fine-grained groundmass are green pleochroic amphibole, lath-shaped feldspar, opaques, and quartz. The majority of phenocrysts are sericitized feldspars. Amygdales are composed of green, pleochroic amphibole encircled by quartz; amphibole in amygdales is petrographically identical to amphibole in the groundmass, but with bigger grains. Occasionally, secondary carbonates are present in amygdala. High-Ti basalts often have a higher percentage of opaques than other Dullstroom types. In certain localities, Dullstroom Formation units contain considerable amounts of biotite. Schweitzer et al. (1995) state that “the lowest portion of the Damwal Formation consists of low-Mg felsites as flows and pyroclastic units intercalated with metasediments and high-Fe, Ti, P volcanics. Petrographic investigations reveal that these units are mostly fine-grained, with pyroclastic, spherulitic, or glassy textures, and are infrequently flow-banded. Some units contain zoned amygdales or secondary quartz veins". Eriksson et al. (1995) have characterized and mapped sedimentary units, which are often metamorphosed and include quartzites. This formation is exclusive to the eastern regions of the Bushveld Complex (Eriksson et al., 1995). 18 | P a g e Kwaggasnek Formation is found across the Bushveld Complex and consists mostly of low-Mg felsites intercalated with sedimentary layers (Buchanan and Reimold, 1998). According to Buchanan and Reimold (1998), "volcanic units are often fine-grained and may exhibit pyroclastic textures, such as lapilli tuffs, spherulitic textures, zonal amygdales, or flow- banding." Several of these units consist of volcanic breccias. Many of the volcanic units feature euhedral to subhedral feldspar phenocrysts that are partly or fully sericitized. Fractures filled with secondary quartz are seen throughout the formation, indicating post-crystallization silicification. The Union Tin Member, which consists of an agglomeration layer overlying a shale, marks the top of the Kwaggasnek Formation. The Waterberg Group's geochemistry has been carefully researched (Faure 1993; Stratten 1986). Clay minerals (kaolinite and montmorillonite or illite), quartz, iron carbonates and iron sulphides, calcite, and trace minerals comprise the mineralogy. Traces of apatite, ankerite, microcline, and anatase were discovered (Faure, 1993). The proximal facies of this slowly sinking shelf platform is coarse, fluviodeltaic sandstone, which wedges out into siltstone and mudstone facies (Pietermaritzburg and Volksrust Formation) in the south (Snyman, 1998). The formation is predominantly formed of coarse-grained arkose, conglomerate, micaceous siltstone, carbonaceous shale, coal seams, and thin layers of limestone (Stratten, 1986). Clay assemblages dominate the mineralogical components of coal samples and are significantly more prevalent in most sedimentary regions. In the Witbank coalfield, these assemblages vary from kaolinite-free to kaolinite-dominated, with subordinate mica and chlorite and small signs of illite/smectite interstratification (Pinetown and Boer, 2006). Examining the link between clay and non-clay fractions based on the presence or lack of kaolinite. Potassium feldspar is more prevalent in kaolinite-rich samples, whereas plagioclase proportions are greater in kaolinite-free samples (Pinetown and Boer, 2006). There is no direct relationship between pyrite and clay minerals, however the presence of pyrite indicates maritime impact or a reducing environment. Mica and chlorite are both considered to be detrital components that originated under conditions of poor chemical weathering, which 19 | P a g e resulted in the lack of kaolinite in an environment containing sea water. The presence of fresh water caused illite/chlorite and smectite to convert into kaolinite (Bühmann & Bühmann, 1988). Apatite and a variety of alumino-phosphate minerals are the most prevalent phosphates in coal and have been detected in a number of coal seams across the world, sometimes in large quantities in certain coal bed sub-sections (Ward et al., 1996; Rao and Walsh, 1997; 1999; Dai et al., 2007). In the cell and pore infillings, apatite and Sr-Ba-Ca-aluminophosphate minerals, occasionally interacting with clay minerals, predominate (Zhao, 2012). At general, accessory minerals occur in modest quantities. Some may be undetectable by XRD and can only be noticed by optical and electron microscopy. In some parts of coal seams, however, accessory minerals may sometimes exist in substantial amounts. Other than iron sulphides, sulphide and associated minerals in coal include sphalerite, galena, millerite, stibnite, chalcopyrite and clausthalite (Spears and Caswell, 1986; Hower et al., 2001; Lawrence et al., 1960; Karayigit et al., 2000; Cressey and Cressey, 1988; Kolker and Finkelman, 1998; Dai et al., 2007). Typically, these minerals precipitate as epigenetic veins generated later in the diagenetic stage, as well as syngenetically in cell and pore lumens, and as discrete crystals in macerals. Boehmite, diaspore, and gibbsite have been detected in coals as Bauxite-group minerals. Al-rich solutions in peat can precipitate gibbsite (Ward, 2002). The Witbank coalfield is located in South Africa's Mpumalanga Province. It is found in the Karoo Basin, which was invaded by dolerite dykes and sills during the earliest stage of Gondwana's disintegration in the Jurassic (about 180 million years ago) (Du Plessis, 2008). The geological units consist of sandstone, carbonaceous shale, siltstone, a small amount of conglomerate, and multiple coal seams (Graham and Lategan, 1931b; Viljoen and Reimold, 1999; Cairncross, 2001; Vorster, 2003). In Figure 2-3, stratigraphic columns are depicted. This large variety of sedimentary and structural contexts was deposited under a variety of ages, climates, and plant life, which resulted in various variances in terms of organic and inorganic content, as well as the degree of maturity of the coal seams (Winter, 1985; Falcon, 1986). The Ecca Group of the Karoo Supergroup sediments were formed on an undulating Karoo floor, which impacted the distribution and thickness of the sedimentary layers as well as the 20 | P a g e coal seams (Pinetown and Boer, 2006). Even though post-Karoo erosion has removed considerable quantities of coal, no more than 180 meters of Karoo strata have been retained. In the region where the thickest Dwyka deposits are found in the deepest palaeo valley, many main glacial valleys are known. Numerous ridges, composed primarily of igneous rocks, with the felsite-lithified ridge forming the southern edge of the coalfield (Pinetown and Boer, 2006). The five seams are confined inside a 70-meter sequence, and the thickness of the separation between seams is rather consistent across the field (Smith and Whittaker, 1986). In the Witbank coalfield, sediments above sills have been moved and raised, whereas layers under sills have remained untouched. The dolerite dykes of the Witbank region display modest vertical displacement. The heat emitted by dolerite dykes and sills hastened metamorphism and depleted coal seams' volatile components. The coal reserves of the Witbank coalfield are found in the Vryheid formation, Ecca group, and Karoo Supergroup. Normal seams in the Witbank Coal Basin are numbered 1 through 5. Typically, coal seams weaken toward minor palaeoridges and finally pinch out against major palaeoridges (Snyman, 1998). Seals interlayers (15-50 m) transgress seams; dykes of 0-1 m thickness are abundant, moving east, northeast, and north; the most significant dyke is the Ogies dyke (15 m thick, 100 km long and strikes east-west) Transgressive sealing interlayers caused the tilting and displacement of seam mining blocks at various altitudes, resulting in significant mining issues. The volume and intensity of coal combustion caused by intrusions provide a significant challenge to mining and resource assessment (Smith et al., 1994; Smith and Whittaker, 1986). The Ecca Group conformably rests on the Dwyka tillite or the pre-Karoo basement is the Rooiberg Felsites (Cairncross, 1989). Figure 2-2 depicts stratigraphic sections for several regions of the coalfields illustrating the coal seams and non-coal layers described before. The sandstones and siltstones vary in coarseness, can be dark or light, and range in thickness from a few meters to 70 meters; they are separated by shale layers and coal seams (Graham and Lategan, 1931b). 21 | P a g e There are five coal seams, as seen in Figure 2-2. Seam No. 1 is the lowest and is either supported by tillite or Dwyka Group shale and sandstone bands (Graham and Lategan, 1931a). Seam No. 1 is patchily developed across the coalfield with the exception of the northern portion of the coalfield, near to the town of Witbank, and the eastern portion of the Optimum and Arnot collieries (Figure 2-3), where it attains a thickness of 3 m. (Pinheiro, 1999). The majority of seam No.1 is comprised of lustrous to dull coal with shaly sandstone partings, resulting in a localized lower seam No. 1 in the Arnot region. According to Pinheiro (1999), seam No. 1 has an exceptionally low phosphorus level and is frequently exploited as a metallurgical feedstock. Falcon (1989) hypothesized that seam No. 1 originated in a freshwater peat bog that covered a platform of sediment produced from an old braided glacial river system. 2.2 WITBANK COALFIELD The South African province of Mpumalanga is home to the Witbank coalfield. It is discovered in the Karoo Basin where dolerite dykes and sills from the early Jurassic period of Gondwana fragmentation (about 180 million years ago) were intruded (Du Plessis, 2008). Sandstone, carbonaceous shale, siltstone, minor conglomerate, and a number of coal seams are among the geological units (Graham and Lategan, 1931a; Viljoen and Reimold, 1999; Cairncross, 2001; Vorster, 2003). Figure 2-3 shows an illustration of stratigraphic columns. There are many variations in terms of organic and inorganic content as well as the degree of maturity of the coal seams due to the vast variety of sedimentary and structural environments in which they