Diagenesis is regarded commonly as effecting only minor changes in a sandstone. However, certain changes in mineralogy and texture can be recognized as responses to physico-chemical conditions similar to those of regional metamorphism, but developed at lower temperatures and pressures. Recognition of mineral associations leads to identification and classification of chemical reactions involved and to reconstruction of the diagenetic environment. The sedimentary history may be reconstructed in reverse order by consideration of three stages: late burial (lithification), early burial, and depositional.

Alterations in cements, mineral replacement relations, and appearance of diagnostic authigenic minerals provide data for interpretation of the reactions leading to the erection of diagenetic isograds, and reconstruction of the condition of late burial. Reactions typical of lithification trend in the direction of reduction in free energy in individual minerals, reduction in water in the crystal lattice, and transformation of clay minerals into more ordered lattices of more definite composition.

With the exception of textural changes brought about by compaction, the environment of early burial is dominated by reactions controlled by Eh and pH. Examples are authigenesis of certain clay minerals, and precipitation of silica, iron oxides, and carbonates in pores or as concretionary growths. Groups of associated minerals representing this stage of development may be plotted in a form comparable with ACF and AKF diagrams. From these can be drawn interpretations of the chemical conditions prevailing.

Paragenetic relations among individual grains permits reconstruction of the composition of the raw detritus. Environments of accumulation represent conditions of important changes in solution, oxidation and reduction. Modification in mineralogy occurs as reactions controlled by Eh, pH, and solubility products occur among the components.

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