Geochemical investigation of the Witbank coalfield using instrumental neutron activation analysis

The No. 2 coal seam of the Witbank basin, South Africa, has a well defined geological layering that extends laterally over most of the basin. Palaeoenvironmental studies indicate that the No. 2 seam accumulated in two distinct depositional environments: glaciofluvial channels and regions represented by transgressive marine sediments. A systematically selected suite of samples was collected to study the distribution of trace elements both laterally and vertically across the No. 2 seam. A total of 121 coal samples were analysed for 15 trace elements by instrumental neutron activation analysis. Detailed trace element profiles across the No. 2 seam indicate that trace elements associated with the inorganic minerals in coal reflect vertical changes in the clastic source areas, environments of precipitation and accumulation or intrusive mineralisation in the post-peat swamp phases of the No. 2 seam. Trace elements associated with the organic matter in coal relate to changes in the palaeoenvironment or possible plant associations. Variation in the concentration of Br across the Witbank basin reflect regional changes in the depositional environment. In turn the chemical nature of the depositional environment strongly effects the distribution of some trace elements among maceral groups. on indefinite secondment to the NPRU