Block modelling of an orebody using surpac- a Case Study at Gold Fields Ghana Limited (GFG)

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The Tarkwa (Underground) Mine of the Gold Fields Ghana Limited has got a limited life span due to depleting underground reserves. This has led to an intensification of search for alternative source of ore for the underground mine This research sets out to apply the Surpac Specialist software to process borehole data from a recently completed diamond drill exploration project at the Kottraverchy area, and to produce a block model of the shallow underground deposit intercepted The research begun with the collection of drillhole data, creation of database, extraction of vertical sections, formation of solid three-dimensional model (3DM) and compositing of drillhole assay data. The main block modelling processes included, the creation of an empty block model, addition of constraints to the model, addition of attribute fields (e.g.. assay, zoning and specific gravity fields), tilling of block with attribute values, extraction of sections, and generation of grade and volume/tonnage report. Finally the grade and volume/tonnage results were manually validated to ascertain their reliability. The total resource of the deposit amounted to about 19.4 Mt at a mean grade of about 1 .5 g/t. At a cut-off of 5 g/t, however, a total of about 0.9 Mt of ore at mean grade of 6.9 g/t was reported. It also came to light that only twenty-two (22) blocks (of size 75 m x 50 m x 5 m) from the two zones of Al of the Ajopa reef and AFc3 of the Kottraverchy reef respectively can be classified as ore at a cut-off 5 g/t.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of Postgraduate Diploma in Mining Engineering, 1997