Basin‐Wide Diagenetic Patterns: Integrated Petrologic, Geochemical, and Hydrologic Considerations

Abstract

The serious scholar of petrology is well aware of the discrepant level of understanding that exists between igneous and metamorphic petrogenesis and sediment diagenesis (also known as postdepositional evolution). While nucleation and crystallization theory, phase equilibria, and principles of heat and mass transport have provided guidance for scientists to understand the formation and subsequent evolution of igneous and metamorphic rocks, sedimentary petrologists seem to have been left behind in detailed, descriptive characterization, with little chemical and physical basis to unify the diagenesis of one rock unit with any other.Of course, one cannot lay blame entirely on the scientist: the study of sediment diagenesis is plagued by problems of incomplete chemical reaction, the need to characterize amorphous solids and poorly crystalline mineral phases, low temperature and pressure conditions that result in reaction kinetics dominating over thermodynamic equilibria, and a lot of fugitive water! Further complications arise because most of the samples available for extensive regional study of sediment diagenesis are those recovered during the exploration and exploitation of hydrocarbon and mineral resources. The processes that have controlled postdepositional chemical and physical evolution of such samples are undeniably nonrepresentative of those affecting the vast volumes of most sedimentary sequences.