Use of termitaria in surficial geochemical surveys: evidence for >125-μm size fractions as the appropriate media for gold exploration in northern Ghana

Abstract

ABSTRACT Extensive lateritization and widespread sheet wash and alluvial deposits characterize the thick regolith in the savannah regions of northern Ghana. As often is the case in these areas, the presence of these cover materials mask geochemical gold (Au) response in soils during surficial gold exploration. Anomaly detection thus becomes very difficult perhaps due to gold grain encrustation during lateritization and anomaly dilution by sheet wash deposits. Termite mound samples collected from areas of thick regolith, transported overburden and laterite cap in gold bearing areas of northern Ghana which were analyzed for gold defined anomalous zones. Gold contents were determined from size fractions consisting of −125 μm, +125–250 μm, +250–500 μm and +500 μm. The gold contents show relatively insignificant changes in concentration and in repeat samples in the −125 μm and +125–250 μm size fractions, but there were significant differences when sub-samples were re-analysed in the coarser samples. Gold content repeatability was relatively better in the fine size fractions (−125 μm) and decreased in the coarser size fractions. The study showed that termite mounds can be used as a geochemical sample medium to support conventional soil surveys especially in areas under thick regolith and transported cover, and the −125 μm size fraction appears the most appropriate.