O możliwości występowania boksytów laterytowych w niecce żytawskiej

Kazimierz Szpila, Zenon Wichrowski



Accumulation of gibbsite was found in gray kaolinite-halloizite clays accompanying brown coals exploited in the Turów I mine. Gibbsite and kaolinite form irregular light-coloured concentrations scattered throught the clay body. Two to three meters below the base of upper coal seam the gibbsite-bearing concentrations markedly increase in number, forming a distinct layer about 40 cm thick (Fig. 1). The occurrence of gibbsite was shown by results of diffractometer (Fig. 2), derivatograph (Fig. 3) and chemical (Table) analyses. The chemical composition of the concentrations indicates that contribution of gibbsite approaches 75%. The gibbsite is genetically related to basic intrusive rocks occurring in the substratum of sedimentary basin of Żytawa basin. It represents a product of intense chemical weathering under tropical climate conditions. The weathering resulted in gradual alteration of primary minerals to secondary layered silicates of the type 2 : 1 and 1 : 1 and finally to aluminium hydroxides. The aluminium hydroxides were hitherto unknown from the deposits of Żytawa basin. Their occurrence makes it possible to assume that conditions favourable for laterite weathering predominated in that area during the Miocene. Therefore it is not excluded that the processes of laterization could resulted in formation of economically important larger accumulations of gibbsite in the areas of occurrence of basalts in Lower Silesia region.

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