diagenetic

Diagenetic refers to the physical, chemical, and biological changes that sediments undergo after deposition and before they become cemented rocks. These changes occur at relatively low temperatures and pressures compared with metamorphism and include processes that alter mineralogy, texture, porosity, and permeability.

Common diagenetic processes include compaction and dewatering, which reduce porosity as overburden pressure squeezes sediments. Cementation by newly formed minerals such as quartz, calcite, or dolomite binds grains together. Authigenesis produces minerals within the pore space, while dissolution and recrystallization can modify grain boundaries and create secondary porosity. Replacement of original minerals by different minerals, formation of concretions, and the development of stylolites or other deformation features also reflect diagenetic work. Organic matter can undergo diagenetic alteration, influencing carbon cycles and hydrocarbon potential.

Diagenesis is influenced by burial depth, temperature, pressure, pore-water chemistry, redox conditions, and fluid flow. Time and sediment composition also play key roles. Diagenetic alterations are typically categorized into stages such as early diagenesis, occurring at or near the sediment surface with rapid chemical reactions, and burial diagenesis, which proceeds as sediments are buried deeper and heated less than metamorphic thresholds.

The term is often used in geology, hydrogeology, and petroleum geology to describe how sediments evolve to conventional sedimentary rocks. Diagenetic changes can either decrease or enhance reservoir quality, depending on whether cementation reduces porosity or dissolution creates secondary porosity.