Comparative quantitative petrographical analysis of Cenozoic aquifer sands in Flanders (N Belgium): overall trends and quality assessment

The bulk mineralogy and grain size distribution of 30 sands of the Belgian Cenozoic were studied. From each sample, the grain size distribution was defined both by classical sieving and image analysis (IA) of thin sections. The grain size distribution by means of automated IA produces an overestimation of the smaller grain sizes; this is related to the artificial breaking up of heterogeneous grains and to the random sectioning of the grains in thin section. However, the results of the quantitative mineralogical analysis of the sands obtained through point counting indicate overall depositional or diagenetical influences. Continentally influenced sands are characterized by a high quartz content, whereas marine-influenced sands reveal a more diverse mineralogy. The potentially reactive chert content generally lies under 2%. Sedimentological and diagenetical influences on the mineralogy and physical properties of the sands thus control the applicability of such materials as building sands.