Statistical analysis of copper and gold assays from drill hole samples from the Chapada copper deposit, Goiás

Abstract

This paper presents the results of statistical analysis of lithological data and copper and gold assays from drill hole samples from the Chapada copper deposit, in Northwestem Goiás, Brasil. Rock descriptions were checked against copper and gold assays in order to verify the relation between host rock and mineralization. Frequency distributions of copper and gold assays were analyzed to obtain an overall estimate of sampled populations and also to attempt a first approximation of the average grade of the deposit. If the Chapada copper deposit were to be mined, it would be done by the traditional method of open-pit bench-cutting, hence the original samples were treated to reflect intervals equal to bench height. These composite assays were statistically analysed in order to verify the validity of compositions. The new frequency distributions dealing with the composite samples when compared with the original distributions are somewhat smoother and more closely approximate normal distributions.