| Popis: |
Fractals are shapes that look basically the same on all scales of magnification — they are self-like. Numerous natural phenomena have this property, and fractal geometry has contributed significantly to their analysis. Geochemical maps and other geochemical data from the literature indicate that geochemical dispersion patterns (geochemical landscapes) may have fractal dimensions because they appear similar at all scales of magnitude from microscopic to continental, in agreement with diverse geological processes of varying rapidity and spatial extent ranging from chemical reactions to continental movements. Analysis of variogrammes and other tests carried out on geochemical dispersion patterns (contents of 21 acid soluble elements in 6000 samples of stream sediment) with a 250,000 km2 survey area in northern Fennoscandia indicates a fractal dimension of between 2.1 and 2.9 for 10 elements (Al, Ba, Ca, Fe, Li, Mg, Sc, Sr, V and Zn), while the remaining 11 (Ag, Ce, Co, Cr, Cu, La, Mn, Mo, Ni, P and Zr) give inconclusive results presumably due, mainly, to inadequate precision of the chemical analyses. These fractal dimensions were found to exist between distances of 5 and 150 km, which are the linear limits set by the sample spacing and the size of the survey area respectively. It is proposed that various sets of geochemical, geophysical and other types of data from around the world be analyzed for their fractal properties, collecting evidence as to whether fractal dimensions are a general quality of geochemical dispersion patterns. If it can be shown that geochemical landscapes are usually true fractals analogoues to topographic landscapes, the impact on applied geochemistry may be profound. One practical consequence in mineral exploration could be the possible existence of numerous economically interesting regional to continental geochemical provinces on earth. Such provinces could be detected at relatively low cost through analysis of wide-spread samples. Consecutive denser sampling within the disclosed provinces would reveal subprovinces, which again could be investigated further by successively more intensive sampling. This type of systematic survey employing the principles of fractal geometry for stepwise selection and progressively more thorough examination of subareas of decreasing size, would apply to any survey area of interest and could improve cost-efficiency in mineral exploration. |
