Geochemical reconnaissance for uranium and base metals using heavy mineral separates in central and southern Sumatra a preliminary report

A reconnaissance drainage survey has been carried out in central and southern Sumatra, primarily for uranium, but also encompassing several base metals. An area of 40.000 km2 has been covered in less than eleven months field work at a cost of less than $1 per square kilometre, using a combination of traditional geochemical methods and the rather less common heavy mineral panned concentrate as sampling medium, followed by tetrabromoethane separation in the laboratory. The results indicate an enhancement of contrast of the heavy mineral separates, as compared to the corresponding ordinary stream sediments. The phenomenon is evident for most of the elements, including the primary target, uranium. It is suggested that Fe and Mn hydroxide coprecipitation of elements is the dominant dispersion process, as opposed to adsorption on clays, and that the dominant means of dispersion will be mechanical, rather than chemical, once the solution transporting the element is exposed to the atmosphere. Several areas have been delineated as worthy of follow-up and this work is proceeding. The importance of such rapid, cheap reconnaissance for the developing countries is underlined. The work can be carried out using semi-skilled field pernosonnel with junior geologist in supervision. One senior qualified project manager is required to coordinante movements, data processing, and sample treatment. (author)