A mineralisation model for the exploration of gold deposits along the Prestea gold belt of south-western Ghana: Case Study at Anfargah and Buesichem

Abstract

The aim of this thesis is to establish a mineralisation model for the gold deposits/occurrences along the Prestea Gold Belt in south-western Ghana. The work is to support active exploration which is currently underway on the belt to find new orebodies and/or extensions to old ones. In modern exploration, a mineralisation model which contains all the attributes of the deposits and explains the causative effects of localisation of minerals in a particular environment is required to save time and money. It is therefore deemed appropriate to design one such model to aid exploration work along the gold belt. The work encompassed geological mapping, sampling, mineralogical and geochemical analyses to validate previous investigations using attributes including: structural controls (openness of structure and attitude of fissure), lithology (type of quartz, meta-volcanic rocks, meta-sedimentary rocks), hydrothermal alteration and ore mineral association which are the main controlling factors of the gold mineralisation on the belt. Since each attribute has varying “parameters” that differently affect the contribution of the attribute to the gold mineralisation, each parameter was assigned a weight according to its reported influence on gold mineralisation. The parameters of the individual attributes are quantified scientifically and expressed in inter-relationship depending on the role or influence on the gold mineralisation process. As the gold mineralisation does not depend solely on an attribute or parameter but rather on the inter-relationship of all the attributes and the parameters, therefore a mineralisation model was formulated to express this inter-relationship in order to predict probable gold mineralisation along the belt to aid exploration. The model for the gold mineralisation was deduced as , where, Y is the gold mineralisation, X parameter variables, β the unknown coefficients and ε the residual mineralisation which is not captured by the mineralisation model. In formulating the mineralisation model, the Analytic Hierarchy Process (AHP) was adopted to provide weights for each criterion as a function which was thereafter inputed into multiple linear regression equations forming a hybrid for the mineralisation model. The mineralisation model was then tested on Buesichem and Anfargah gold deposits. The model showed that the Buesichem deposit is good whilst Anfargah fair. The study thus concluded that the model may be applied to distinguish between poor and good gold prospects along the belt.