Origin and forms of occurrence of silica in Riphean deposits of the Baikit Anteclise (Siberian Platform) in connection with the problem of formation of fracture-cavernous collectors

The Riphean dolomites in the southwest of the Siberian Platform contain no less than 5% siliceous material quite irregularly distributed over the section. The siliceous material was accumulated at different stages of lithogenesis. Many syngenetic accumulations of silica are confined to beds of organogenetic and organogenetic-clastic dolomites. In the course of postsedimentary transformations, the siliceous material was redistributed. The climax of these processes was reached in the period of the pre-Vendian gap in sedimentation and karsting of the dolomite suite. The accumulation and redistribution of silica had a great effect on the formation of the fracture-cavernous collector in a producing suite within the Baikit anteclise of the Yurubchen-Tokhomo zone of petroleum accumulation.