ELEMENTAL COMPOSITION AND NUCLEAR PARAMETERS OF SOME COMMON SEDIMENTARY MINERALS

Major and trace element chemistry has been used to investigate critica l characteristics of 89 specimens of 15 minerals that are commonly fou nd in sedimentary rocks. For kaolinites, Na+, Mg2+ and Ca2+ are exchan geable cations while other elements are essentially non-exchangeable. The compositional variability of most minerals is seen to be quite low (even for clay minerals) which bodes well for resolving the mineralog y of formations from down-hole elemental data. Nuclear parameters such as the photoelectric absorption cross section, natural gamma-ray acti vity, thermal neutron absorption cross section and neutron porosities calculated from chemical analyses of minerals often exceed values calc ulated using simple chemical formulae.