Sediment Mineralogy and Geochemistry

Insight in the mineralogical and the geochemical composition of Dutch geological sediments is needed for environmental management of the subsurface. A comprehensive overview of these compositions is given in this chapter. The first part of this chapter deals with the mineralogy of the Paleozoic and Mesozoic sedimentary rocks where properties of the rocks are discussed per stratigraphic period. The information presented is mainly based on studies that had a commercial interest in exploring and exploiting the associated natural resources, which gives some indication of what has been studied. The detrital versus diagenetic origin of minerals is considered as fully as possible. The second part covers the Cenozoic, unconsolidated sediments where both the mineralogical and the geochemical compositions are considered. The studies that are summarized were diverse in scope and dealt with the soil and deeper Cenozoic sediments. The sediment geochemical composition is first considered based on results of factor analysis, which has frequently been applied in sediment-geochemical studies. Next, individual elemental relationships are presented for several minor elements. Then the mineralogy is briefly considered for quartz, feldspars, heavy minerals, clay minerals and carbonates, whereby notable differences as well as similarities are discussed. Finally, four specific features are discussed that are worth to be summarized from an environmental perspective: bog iron ores, trace elements in pyrite, sulphur in peat, and lead and its isotopes in soils.