Kenya regional geochemistry

The Samburu - Marsabit Geological Mapping and Mineral Exploration Project was a joint Kenyan and British technical co-operation project, carried out by staff of the Mines and Geological Department, Ministry of Environment and Natural Resources, Kenya and staff from the British Geological Survey. The first phase of the project commenced in 1980, and covered the area between 36degrees and 38degrees E and from the equator to 2degrees N. The second phase, carried out between 1984 and 1986 covered the area between 36degrees and 38degrees E and from 2degrees N to the Ethiopian border. Sampling was carried out concurrently with geological mapping and was largely constrained by the requirements of that exercise. Little or no sampling was done in areas previously mapped by other bodies. Sampling was mainly confined to areas underlain by basement rocks of the Mozambique Belt and was very sparse over most of the Tertiary and Quaternary volcanic cover. Chemical analyses for the stream sediments were: Ag, Ba, Co, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sr, and Zn. Raw data is available from the Mines and Geological Survey Department, Ministry of Environment and Natural Resources, Nairobi, Kenya. Sampling densities varied considerably across the Phase 1 project area, but generally a stream sediment sample density of one per 4 to 8 km2 and a panned concentrate density of one per 13 to 16 km2 was achieved. In the Phase 2 area, which was mainly very arid, a few samples were collected from dry stream beds, as part of a helicopter survey of the area, to provide some idea of the geochemistry of the major lithological units. Stream sediments were collected by combining grab samples from 5 to 10 points within a 10m radius of the selected site. If necessary the samples were dried before being sieved and the fine (-80 mesh B.S.) fraction retained for analysis. Heavy mineral concentrates were obtained by taking 2 to 5kg of material from the sample site and panning at the base camp, where water was available, or at the Mines and Geological Department headquarters at Nairobi.