Diagenesis

The diagenesis (from gr δια, by, through and γένεσις emergence, formation) is the geological process of consolidation of loose sediments such as mud and the change of the rocks under relatively low pressures and temperatures up to their removal.

This is done in three steps: after the early diagenesis already during the deposition of the compaction and cementation. The compaction arises as soon as the sediment is pressed and drained a large load of the upper rock strata. With the pressure, the temperature increases slightly. In the cementation form in the pores of the rock new minerals and it solidifies by dissolution of minerals ( mainly carbonates, such as limestone ) and others after Rieck ash principle, material diffusion and crystal formation. Both processes can run simultaneously.

For loose sand is so hard sand stone. Another example is the formation of flint from silica enrichments in limestones or the formation of fossils of animal and plant residues ( fossilization ). The formation of oil and gas from kerogens also takes place during the diagenesis. The diagenesis may already during the deposition of loose sediments begin ( early diagenesis ). However, it can also be used at any time, from the deposit to the removal of the rock again and the rock change ( Spätdiagenese ). It is thus a part of the cycle of the rocks.

The distinction between diagenesis and metamorphism is blurred, because the metamorphosis also describes the process of rock alteration as a function of pressure and temperature. However the pressures and temperatures are by far occur during the metamorphosis are higher than those of diagenesis. This results in the metamorphosis usually to significant changes of mineral deposits or rock structure that does not take place in the diagenesis so.