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The article considers the distribution of different ages volcanic formations of Elbrus volcano, PaleoElbrus and autonomous eruption centers within the modern volcanic structure of Elbrus and its environs. The proposed generation sequence of these volcanogenic formations is shown, which was established using the geomorphological method by the morphology of the lava flows’ surface, as well as by the ratio of volcanogenic formations to each other, with Quaternary deposits of other genetic types, and with landforms.

Based on new materials, the structure and origin of a huge (up to 2-km-thick) massif of acid volcanic rocks, which occur in the volcanotectonic depression in the upper reaches of the Chegem River in the North Caucasus, is considered. The issue of the lava, rather than the pyroclastic origin of the main part of the massif, is discussed. This massif was formed due to multiple eruptions of lava flows that composed a series of the acid volcanic rocks without gaps and with a well-pronounced columnar jointing in a limited volume of a deep volcanotectonic depression formed synchronously to eruptions in the Late Pliocene. The volcanic rocks were formed as a result of the boiling of a silicate melt and its exit from the vent of the volcano, which could be due to the phase transition of a supercritical aqueous fluid.

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.

We present the first results of fission-track dating of apatite monofractions from two rock samples taken from the Southern carbonatite massif of the world’s largest alkaline ultrabasic Guli pluton (~250 Ma), located within the Maymecha-Kotuy region of the Siberain Traps. Based on the apatite fission-track data and computer modeling, we propose two alternative model of the Guli pluton's tectonothermal history. The models suggest (1) rapid post-magmatic cooling of the studied rocks in hypabyssal conditions at depth about 1.5 km, or (2) their burial under a 2-3 km thick volcano-sedimentary cover and reheating above 110°C, followed by uplift and exhumation ca. 218 Ma.

This work describes a young extrusive massif in the uppermost reaches of the Chegem River (Bashilauzu-su River), which had been considered as a feeder of the great sequence of Upper Pliocene rhyolite ignimbrites of the Verkhnechegemskaya caldera. The Upper Pleistocene age of the stratum, extrusive origin of automagmatic breccias and fluidolites, as well as its difference from rhyolites of the caldera are proven. The Bashilsky swell, located in the Late Pleistocene glacial trough, is evidence of young volcanism in this area, which has not been previously proposed.

Four glass types, which sharply differ in terms of their silica content and the K2O/Na2O ratio are found in the earliest eruption products of the Bityuk-Tyube independent eruption center in the Western Cis-Elbrus Region. In addition to this, two monomineral glasses, which are close to monomineral plagioclase and quartz types, are identified. Such a composition of initial melts was produced by deep fluid explosions. It is shown that deep fluid explosions, on the one hand, initiate substrate melting and, on the other hand, prepare and develop channels for the further eruption of igneous material.

Fluidolite, a new genetic rock type that was formed under the leading role of the deep decompression fluid explosions, was first revealed in the Northern Prielbrusye. The geological position, textures, structures, and peculiarities of the petrographic and chemical composition of fluidolites are described.