Structure of Basic Clay Mineral Groups, and Interpretation of Clay Mineral Data
Clay minerals as a group are largely phyllosilicates, therefore this discussion will be more or less limited to the latter. Silicates are made of SiO4 -4 ionic groups in combination with metallic cations. Oxygen ions are much larger in size than most of the cations, so volumetrically oxygen makes up the bulk of silicates. Silicate minerals, indeed the entire earth's crust, can be visualized as being made of close-packed oxygens with the smaller cations filling the interstices. This is not unrealistic, since oxygen constitutes 94% by volume of the earth's crust.
Figures & Tables
Clay Minerals for Peteroleum Geologists and Engineers
These notes provide a general introduction of clays for the uninitiated, plus a review of traditional and more recent concepts for those who already know something about clays. The concept of fundamental illite particles and the phenomen of interparticle diffraction, relatively new concepts that are reshaping the manner of visualizing mixed-layer clays, are discussed in some detail. A discussion of shaly-sand log analysis, from a clay mineralogy perspective, is included. Isotope geology is discussed because of its potential for permitting a better understanding of temperatures and timing of diagenesis.