This study was carried out on the main coal-producing and the extensively block-faulted area of Mchenga Coal Mine, southeast of the 90 km2 intracratonic Livingstonia Coalfield in the north of Malawi. It was initiated against the background of indistinct information on coal geology, shortage of energy and potential environmental threats due to mine activities. The study aimed at integrating investigations of characterization of the lithostratigraphy, coal seam correlation, coal quality determination, examination of the mineralogy and geochemistry of coal and hosts rocks, assessment of water quality and providing information for mining and potential environmental and water quality impact assessment in the study area. The methodologies used in this study include literature review, field visits, mapping, sites selection and characterization, borehole logging, geochemical analyses, data processing and interpretation. The geochemical analyses include proximity analysis of coal quality, microscopy and X-ray Diffraction for mineralogy and petrology, X-ray Fluorescence (XRF) for rock geochemistry and Atomic Absorption Spectrometry for determination water geochemistry. The results have shown that a) The Coal Measures comprises of four to six coal seams in different localities, and the occurrence is flat and gently dipping southeast and are correlated. Thicknesses of the coal seams vary from 0.10m to 3.0m with some notable lateral and horizontal variations. Thick and workable seams occupy the lower portion of the Coal Measures and are exposed along the North Rumphi River bank; b) Coal quality belongs to sub-bituminous ‘A’ to ‘C’ on ASTM classification (1991), being characterised by low moisture content (0.8 to 1.3 wt percent) and sulphur content (0.49 to 0.85 wt percent), high ash content (9.0 to 17 wt percent) and volatile matter (24 to 32.9 wt percent), fixed carbon (53.6 to 62.6 wt percent), calorific value (7,015 to 7,670 kcal/kg); c) Mineral matters constitute approximately 9.55 to 38.34 wt percent of the coal samples, predominantly clays (interstratified illite/smectite and kaolinite) with varying proportions of quartz, mica and feldspars, as well as minor calcite and pyrite and their geochemistry, being characterised by enrichment of SiO2 from 5.37 to 20.56 wt percent, Al2O3 (2.63 to 11.21 wt percent) and K2O (0.32 to 3.65 wt percent) with trace concentrations of CaO (0.04 to 0.41 wt. percent), MgO (0.08 to 0.65 wt percent) and P2O5 (0.018 to 0.037 wt percent) and Na2O concentration notably below 0.01 wt percent; d) Calcite and pyrite constitute minor concentration in both sandstones and shales; e) Water quality in the area is characterised as two groups of acidic (pH 3.3-6.4) and near-neutral to slightly alkaline (pH 6.9-7.3) and low pH, high TDS, SO42- and EC are noted at the coal crusher plant which points out to high leaching of trace elements such as Pb and Fe. Na++K+ are dominant in upper sections of North Rumphi and Mhlepa Rivers. Ca2+ cations are dominant at crusher plant, underground mine and lower section of Mhlepa; f) Based on the geochemistry analysis, Na and trace elements such as Ti, V, Mn, Fe, Zn, Rb, Sr and Zr from coal and host rocks have the ability to contribute significantly to deterioration in the ground and surface water quality in the study area. It can be concluded that the coals of the Livingstonia Coalfield belong to Gondwana group deposited in sub-basin with multiple seams embedded in sandstone and shale host rocks.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufh/vital:11518 |
| Date | January 2012 |
| Creators | Maneya, George Jameson |
| Publisher | University of Fort Hare, Faculty of Science & Agriculture |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Masters, MSc (Geology) |
| Format | 139 leaves; 30 cm, pdf |
| Rights | University of Fort Hare |
Page generated in 0.002 seconds