Abstract

Field studies, in particular mobile metal ion analysis of soil samples taken over mineralization, suggest that subtle geochemical anomalies exist above mineral deposits which are demonstrably covered by allochthonous material such as glacial till. Empirical observations suggest that the anomalies are preferentially located 10 to 25 cm below the soil interface, comprise elements contained in ore, and are located directly above the mineralizing source. Laboratory experiments suggest that capillary rise and evaporation play an important part in determining the position of emplacement of ions in the soil profile: in nature, root-zone transpiration also plays a part in solute deposition/adsorption within the evapo-transpiration zone. The effects of downward-percolating water after rainfall events, as well as the upward force of capillary rise, are considered in a model which explains many of the features of ion emplacement in soils. Laboratory modelling also suggests that convection, perhaps due to the heat produced by oxidation of the deposit, may in some cases provide a mechanism for rapid ascension of ions beneath the water table.

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