Use of Multi-Media Sampling as Integrated Approach to Surficial Geochemical Sampling for Gold in Regional Reconnaissance Surveys in Parts of the Ashanti Belt, Southwest Ghana

Abstract

This study compared the conventional method used in surficial geochemical sampling to multimedia sampling method during reconnaissance surveys in gold exploration. The use of the conventional method in regional reconnaissance exploration surveys whereby surficial geochemical sampling is done step-wise, first by sampling stream sediments followed by rock chips then soils and other regolith materials in the search and defining of prospective targets of gold mineralization appears inefficient in geological environments characterized by complex regolith and landform modifications. However, multi-media geochemical sampling which involves the simultaneous sampling of different geochemical samples appears a better alternative and eliminates false and erratic anomalies often associated with the sampling of a single medium. Multi-media samples comprising rock chips, scree, termite mounds and lateritic lags, were collected simultaneously to support stream sediments in parts of the Ashanti belt in the Birimian of southwest Ghana, which is characterized by complex regolith and landform modifications. The most prospective targets among the three anomalous zones defined by the stream survey were better pronounced with the support of the other media, based on the consistency in significant gold contents in those samples. Gold assay values from the multi-media samples ranked the Manso East target as the most prospective and the Manso Northwest target being least prospective due to the inconsistent gold assay values in the different media. Thus the integration of the gold assay values from the various media defined real and prospective geochemical gold targets better than in the conventional method in which sampling of different media was done in stages. Unlike the conventional method, the multi-media survey provided gold results that showed regional, proximal and in-situ anomalies simultaneously. Multi-media geochemical survey therefore, appears to be a reliable method that can be used in regional surficial geochemical exploration for gold in areas characterized by hidden anomalies.