Overbank sediments as appropriate geochemical sample media in regional stream sediment surveys for gold exploration in the savannah regions of northern Ghana

Conventional stream sediment sampling in which sediments are taken from the active channels during reconnaissance regional geochemical surveys in gold exploration has over the years failed to delineate prospective target zones in northern Ghana, where the relict is flat. Whereas the technique has been successful in the south western Ghana, which is characterised by moderate to high relief, generally the savannah north is associated with low relief, commonly with flat topographies and generally decoupled stream channels. Geochemical comparison of active stream and overbank sediments in this study demonstrate that active stream channels may contain contaminated materials of recent origin, but overbank sediments, except for the uppermost horizons, represent alluvial regolith of earlier depositional cycles over time. Based on gold value repeatability, composite samples taken from the overbank sediment layers were relatively less erratic and are considered to be an appropriate geochemical medium in delineating potential regional gold targets for follow up. The results show that overbank sediment sampling can be used as a cost-effective method to define broad anomalous zones; and the technique must be considered useful during reconnaissance geochemical surveys in the savannah regions.