Dispersion of copper and associated trace elements in a Kalahari sand environment, northwest Zambia
In north-west Zambia, Kalahari Sand of aeolian origin forms a cover of varying thickness on residual latosols. Sedimentological and mineralogical characteristics indicate that the Sand is similar to Kalahari Sand occurring elsewhere in southern Africa, and to aeolian sands in general. Geochemical sampling at 9 inch depth on residual soil defines Cu anomalies overlying Cu mineralisation in bedrock. At two localities, the surface Gu anomalies have been extended into Kalahari Sand overburden by the use of the silt fraction for analyses. In both areas, Cu anomalous Sand overlies poorly mineralised bedrock. The Cu, Pe, Mn and Zn content of Kalahari Sand is considerably lower than in soil. Metal patterns in the Sand appear to be epigenetic and reflect variation in bedrock content. Lateritic horizons are widely developed in the residual soils, Kalahari Sand and davnbo sediment, and result in concentrations of Pe, Gu, iin, Zn and other trace elements. In the absence of laterite development, the distribution of metals in Kalahari Sand and some soil profiles displays an upward increase in content. This, together with the epigenetic anomalous patterns, is believed to result from seasonal upward migration of metal-bearing moisture during the dry season. Analyses of grain size fractions of residual soil, Kalahari Sand and dambo sediment indicate that metal content increases with decreasing grain size. Maximum Cu contrast occurs in the silt fraction. Metal values in humus are generally similar to overburden values but greater than the vegetation content. Metal values of termitaria are similar to A horizon values of the overburden. A geobotanical survey reveals no significant variation in tree frequency related to Cu anomalous overburden. Randomly selected common tree species reveal a Gu correlation with surrounding Kalahari Sand values, with maximum content and contrast in bark.