Mineral resource estimation of alluvial Gold deposits - a comparative study

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Nkroful Mining Ltd has acquired a concession at Nkroful town which has both hard rock (vein type) and alluvial gold mineralization. The alluvial gold mineralization is erratic and complex so it demands a thorough investigation to establish the geological characteristics of the deposit and a good estimation method to estimate the gold resource potential of the deposit. This thesis is aimed at, studying the geological characteristics of the deposit and selecting an appropriate mineral resource estimation method through a comparative study of various estimation methods. The outcome should assist Nkroful Mining Ltd in estimating the gold resource potential of the concession and also contribute towards the improvement of alluvial gold resource estimation in Ghana. The geological characteristics of the deposit were studied through literature review and geological mapping in the field. Statistical and geostatistical analysis were used to check and quantify some of the parameters obtained from the geological studies. Based on the geological characteristics of the deposit and sample grade values, four blocks were demarcated for the resource estimation. Triangular, sectional, inverse square distance, statistical and geostatistical methods were used to estimate the gold potential of the deposit. Grade estimates from the various estimation methods did not differ significantly. Comparatively, statistical - estimation - gave higher values. Triangular and sectional estimation gave values that fluctuated between high - and low grades. Geostatistical and inverse distance estimation gave values that were average and compared favourably to each other. Despite the constraint that mined figures were not available at the end of the research work to substantiate the method chosen, it is still proposed that inverse distance square method should be adopted by Nkroful Mining Ltd due to its simplicity and comparability with the geostatistical method which took into account the regionalization of the variables.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfilment of the requirements for the Master of Science (MSc) Degree in Mineral Exploration,1995.