The formation and genesis of the rhyolite series of the Upper Chegem Highlands (the North Caucasus)

On the basis of new materials this article deals with the structure and origin of a huge (up to 2 km) thick massif of acidic volcanic rocks located in a volcanic-tectonic depression in the Upper Chegem River in the North Caucasus. Discussion on the lava’s, rather than pyroclastic, origin of the main part of the rock mass as a result of repeated outpourings of lava flows, which formed the series of acidic volcanic rocks without interruptions with perfectly pronounced columnar jointing in a limited volume of a deep volcanic-tectonic depression, which was forming simultaneously with eruptions in the Late Pliocene. Volcanic rocks formed as a result of boiling silicate meltas the exit from the vent, which could be due to the nature of the phase transition of the supercritical water fluid.