2015. "Diagenesis: Dissolution", A Color Guide to the Petrography of Sandstones, Siltstones, Shales and Associated Rocks, Dana S. Ulmer-Scholle, Peter A. Scholle, Juergen Schieber, Robert J. Raine
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This chapter deals with the removal of minerals from sandstones and mudrocks during any stage of diagenesis by pore waters undersaturated with respect to one or more minerals. Dissolution has long been known to be important in “more soluble” rocks, especially carbonates and evaporites, but the past five decades have seen a growing understanding that it is an important process in clastic terrigenous deposits as well. It should not have been a surprise—sandstones and mudrocks can comprise many different minerals, detrital as well as authigenic, that were formed under a wide range of conditions. Subsequent eogenetic, mesogenetic and telogenetic diagenetic environments subject minerals to varied temperatures and pressures and especially to diverse water chemistries that potentially can range from nearly pure meteoric water to hypersaline brines and from acidic to alkaline. As a result, one can find instances of dissolution of almost any mineral. Widespread dissolution of common grains and cements may have a significant impact on the ultimate composition of terrigenous rocks, their porosity and their reservoir potential.
Figures & Tables
AAPG Memoir 109 is designed as a practical guide for students and professionals to learn the fundamentals of microscopic examination of sandstones, mudrocks, and associated rocks. With more than 1100 color illustrations, it covers the identification of grains, textures, and structures of clastic terrigenous rocks as well as their diagenetic alteration (compaction, cementation, dissolution, and replacement) and porosity reduction or enhancement. It also provides classification diagrams for formal description of those rocks and their porosity. Although the majority of the outcrop and subsurface examples come from the United States (35 states and Puerto Rico), there are representative photographs from 32 other countries, including many from the offshore areas. The foldout birefringence chart and an included DVD with Powerpoint files of all of the petrographic images provide additional aids for instructors and students.