Silicification in the Devonian limestones of the Holy Cross Mts and Silesia-Cracow region

Widespread occurrences of silica in the Devonian limestones of the Holy Cross Mts and Cracow-Silesia region are recognized as the product of superimposed processes which probably occurred during later diagenesis. The two main stages ofsilicification were most likely separate events resulting from progressive calcitization of opaline skeletons and secondary silica remobilization. Older (?pre-Permian) silicification(s) are associated with silica migration toward deposits rich in preferred skeletal grains; it can be seen in replaced fossils. as well as in replacive and drusy quartz megacrystals. The chertlflcauon is a surprisingly young, post-tectonic phenomenon, as indicated by a vein-type occurrence and substitution of late calcite veinlet networks paired with a very low maturity of the silica. This event was associated with a profound disturbance of physiochemical equilibrium within the rock massif (?after Laramide uplift); links to primary opal-rich facies point to extremely short-...