What is anchizone in geology ?

Anchizone - Metamorphism

Metamorphic facies diagram
Anchizone is a transition zone between diagenesis (consolidation of sediments) and metamorphism. The temperatures are low (100 to 200°C) and the pressures below 0.1 GPa, which results in very discrete mineral reactions, visible only in the field of clay minerals (kaolinite, illite, chlorites) and zeolites. Slates generally belong to anchizone.