Singularity analysis of ore-mineral and toxic trace elements in stream sediments

Abstract

Hydrothermal processes in the Earth's crust can result in ore deposits characterized by high concentrations of metals with fractal or multifractal properties. This paper shows that stream sediments in the neighborhoods of ore deposits also can have singular properties for ore-mineral and associated toxic trace elements. We propose a new local singularity mapping method for assembling element concentration values from stream sediment samples to delineate anomalous areas induced by buried mineral deposits, which are often missed in ordinary geochemical surveys and mapping. Applied to the Gejiu area, Yunnan Province, China, which contains world-class size hydrothermal deposits enriched in tin and other elements, non-linear anomalies for tin and arsenic are identified: (1) many relatively small singularity anomalies in about 10% of the study area; and (2) a large high-concentration anomaly in the eastern part of the area where mining occurs. The ore-mineral and toxic elements within these anomalies describe Pareto-type frequency distributions. Spatial proximity of anomalies of the first kind to the ore deposits (mines and prospective mines) indicates that singularity mapping provides a useful new tool for mineral prospecting. The relation of the second kind of anomaly to mining activities indicates that fractal modeling also can provide useful input for decision-making in environmental protection.