Geostatistical estimation of a paleoplacer deposit with hard geological boundary: case study at Tarkwa Gold mine, Ghana

Ansah, Solomon Kwabena (2018) Geostatistical estimation of a paleoplacer deposit with hard geological boundary: case study at Tarkwa Gold mine, Ghana. Masters thesis, Memorial University of Newfoundland.

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Abstract

Geostatistical estimation requires the definition of geological domains by using geologic variables or structural information. The misclassification of the estimation domains may have a significant effect on the resource estimate such as dilution, oversmoothing, undersmoothing of gold grades. In this project, detailed geological modelling coupled with statistical analysis is carried out to aid in the definition of 3 geological domains with hard boundaries. A hard boundary is characterized by an abrupt variation of grade along the boundary between two lithological contacts. The A1 reef in Akontasi east of the Tarkwa Gold mine concession was investigated out of the 7 stratified reefs. The drillhole data considered were obtained by reverse circulation and diamond drilling with ordinary kriging being the preferred estimator for the deposit. Semi-variograms were generated for all 3 domains and estimation within the domains were cross validated and results showed a high Correlation Coefficient. An alternative case was also analyzed, where all three domains were combined and showed a low Correlation Coefficient. Results indicate that the division of the orebody into separate homogenous domains produce accurate results with a high level of confidence.

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