diageneticdepositional

Diageneticdepositional is not a standard term in geology; in practice, discussions of diagenesis focus on the physical, chemical, and biological changes that sediments undergo after deposition and before metamorphism. The phrase is sometimes used informally to refer to diagenetic processes that occur during or immediately after deposition, i.e., early diagenesis, when sediments remain near the sediment–water interface or within shallow burial.

Early diagenetic processes include compaction, chemical cementation by minerals such as calcite, quartz, or dolomite, and the formation of authigenic clay minerals. Recrystallization and dissolution mediated by pore waters can create or remove primary porosity. Redox changes, pH, temperature, and the composition of pore fluids govern which minerals precipitate or dissolve and at what rates. These changes may occur rapidly after deposition and can continue for thousands to millions of years as burial depth changes.

Depositional environment influences diagenetic pathways. Sandstones often experience quartz overgrowth cementation or calcite cementation; carbonates are prone to early carbonate cementation and, in some settings, dolomitization. Evaporite-bearing sediments may undergo dissolution or the growth of sulfate minerals. The cumulative effect of these processes is to modify texture, mineralogy, porosity, and permeability, thereby affecting reservoir quality and rock strength.

Diagenetic-depositional processes are distinguished from metamorphism by the absence of regional high-grade metamorphism and by the dominance of chemical weathering and burial reactions rather than recrystallization under high temperatures and pressures.

Methods used to study these processes include petrography, X-ray diffraction, electron microscopy, stable isotope analysis, cathodoluminescence, and fluid inclusion studies to characterize diagenetic textures and interpret diagenetic histories.