Geochemical prospecting for ores; a progress report

Principles of geochemical prospecting

“…Details of some of these surveys have been published. See items numbered 4, 5, 22, 23, 26, 27, 36, 59, 66, 85, 94, 103, 104, 108, 110, and 117 abstracted by Harbaugh (1953) and also the following: Fersman, 1939;Gilbert, 1951Gilbert, , 1953Hawkes, 1954;Huff, 1952;Kennedy, 1952;Nackowski, 1952;Pierce and Dias,. 1950;and Shima, 1953e, 195314 Much of the work, however, has been sponsored by private mining companies as part of their exploration program, where commercial considerations prevent the release of information to the public.…”

“…Sampling alluvial cover over a lead-zinc vein in the Abakaliki district of Nigeria (Hawkes, 1954) showed a well-defined zone of -lead-and zinc-rich material immediately above the surface of bedrock leading away from the suboutcrop of the ore in the direction of the drainage channel; on the other side of the suboutcrop, away from the drainage channel, this pattern was lacking. Presumably the movement of ground water here was controlled largely by the bedrock surface, as the underlying shale was unweathered and relatively impermeable to percolating solutions.…”

“…A well-defined example of a diffusion pattern was mapped in detail in the Abakaliki lead-zinc district, Nigeria, where relatively unweathered bedrock was overlain unconformably by a 6-foot deposit of alluvial silt (Hawkes, 1954), Sampling on a vertical section through the silt as exposed in an exploration trench showed an easily contoured distribution of zinc, falling off uniformly with distance from the underlying source from a maximum of several thousand parts per million directly over the ore to several hundred at the surface. Historical evidence indicates that the silt in which this pattern was formed was deposited about 400 years ago, so that an estimate of the time required for the evolution of a diffusion pattern can be made.…”

“…No systematic geochemical prospecting surveys based on determination of the unstable components of stream sediments have been published, although a few writers have observed dispersion patterns in drainage channels that can 'probably foe attributed to this cause. Hawkes (1952) mentions cobalt in the sediments of streams draining mineralized areas in the Blackbird cobalt district of Idaho. White and Alien (1954) found more than 500 ppm copper in the soil of drainage channels below copper-rich dumps at Phoenix Camp, British Columbia.…”

“…In 1949, Roberts (1953 working in Nigeria carried out the first experiments with geochemical soil surveys in tropical terrane. Roberts' work was followed by further experiments in the same areas of Nigeria by Webb andMillman (1950, 1951) and Hawkes (1954). Beginning about 1952, several of the large mining companies undertook experimental soil sampling programs in Rhodesia and Tanganyika, many of.…”