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An isotope-geochronological study for a number of young volcanic localities in the eastern part of Balkaria (North Caucasus, Russia), referred to the Neogene–Quaternary stage in the evolution of the Greater Caucasus by previous researchers, was carried out. The results of the K–Ar dating obtained have proved for the first time that volcanic activity was intense in the Late Cenozoic within the territory of modern Eastern Balkaria. It has been established that the young igneous rocks of the Pliocene (4.7–4.0 Ma) Tsana Formation with various compositions (basaltic trachyandesite, dacite, and granodiorite-porphyry) are the most common in the considered region. The area of presence of the rocks of the Tsana Formation was specified within the Russian territory of the North Caucasus. Based on the new isotopic data, the territory that is prospective for exploration of Au–As–Sb–Sn–Mo deposits often associated with young plutonic bodies of potentially ore-bearing Tsana Formation was localized. A new locus of Late Quaternary magmatism where the andesite lava flow was formed ~800–700 ka in the paleovalley of the Udursu River (near the foot of Mt. Cheget-Dzhora) was identified within the Greater Caucasus. [ABSTRACT FROM AUTHOR]

The products of the activity of the Late Quaternary Kazbek neovolcanic center in the Greater Caucasus are studied by isotopic-geochronological methods. It is found that the youngest magmatism evolved during the last 400-450 k.y. over four discrete phases: 395-435, 200-250, 90-120, and less than 50 ka. The petrological-geochemical and published isotopic data point to the mixed mantle-crustal origin of the Kazbek lavas with the leading role of crystallization differentiation of deep magmas and assimilation of the crustal material. We recorded two episodes (∼100 and less than 50 ka) of replenishment of the subsurface magmatic chamber under the Kazbek center by the main mantle melt and its mixing with the relict dacite magma that led to the formation of highly mobile hybrid andesite lavas and served as a trigger of the renewal of volcanic activity. Reactivation of the mantle source of the Kazbek center at the end of the Neopleistocene and the Holocene age of the last eruptions indicate the potential danger of this region because of the renewal of the volcanic activity. The medium Devdoraki copper deposit is located in the vicinity of the Kazbek volcano. It represents a unique polychronous, currently evolved ore-magmatic system that originated in the Jurassic. [ABSTRACT FROM AUTHOR]

New isotope-geochronological data (K-Ar, Rb-Sr) provide tight geochronological constraints on the history of Late Cenozoic magmatism on the southern slope of the Greater Caucasus. Several previously unknown, rhyodacite intrusive bodies with an emplacement age of 6.9 ± 0.3 Ma (Late Miocene) are reported from the Kakheti-Lechkhumi regional fault zone in the Kvemo Svaneti-Racha area. Therefore, a pulse of acid intrusive magmatism took place in a period previously considered amagmatic in the Greater Caucasus. The petrological, geochemical, and isotopic data suggest that these rhyodacites are produced by crystallization differentiation of mantle-derived magmas, which are similar in composition to Miocene mafic lavas that erupted a few hundred thousand years later in the adjacent Central Georgian neovolcanic area. The presented results allow the conclusion that the volcanic activity within the Central Georgian neovolcanic area occurred at 7.2-6.0 Ma in two discrete pulses: (1) the emplacement of acid intrusions and (2) the eruption of trachybasaltic lavas. The emplacement of rhyodacite intrusions in the Kvemo Svaneti-Racha area marked the first pulse of young magmatism on the southern slope of the Main Caucasus range and simultaneously represented the second magmatic pulse (after granitoid magmatism of the Caucasian Mineral Waters region) within the entire Greater Caucasus. [ABSTRACT FROM AUTHOR]

This paper reports on isotope-geochronologic, petrologic, and isotope-geochemical (Sr-Nd) studies of Quaternary magmatism in the Geghama neovolcanic area, Armenia, Lesser Caucasus. According to these studies, the period of youngest volcanic activity in the region lasted about 700 000 years, from 700 ka to a few tens of thousands of years ago. We found the time limits of five discrete phases of Quaternary volcanism: I (about 700 ka), II (550−480 ka), III (190−150 ka), IV (110−70 ka), and V (later than 50 ka). These phases seem to have lasted a few tens of thousands of years and were separated by quiescent periods of comparable durations. The petrologic and isotope-geochemical characteristics of Geghama effusive rocks show that they belong to the bimodal association rhyolite-trachyandesite and basaltic trachyandesite; this association was largely generated by fractional crystallization of primary basite melts, with the assimilation of crustal material by deep magmas being much less important. The isotopic parameters of the volcanic rocks studied here (0.70410-0.70437 for Sr/Sr and +3.3 to +4.0 for Є) are practically identical for intermediate to basic and acid varieties in this association and are similar to those for young basites in the other areas of the Lesser Caucasus; this circumstance indicates a common origin for all Quaternary magmatic formations in the region. The petrogenesis of these varieties probably involved a single mantle source of the OIB type with certain regional peculiarities in the composition of the melts it generated. An analysis of the locations of Quaternary volcanoes in central Armenia (Geghama and Aragats areas) and in the Kars plateau, which is adjacent to it in the west, provided evidence of an eastward lateral migration of youngest magmatic activity in the region over time. The latest episodes of this migration took place in the eastern Geghama area, which must be the first to produce eruptions in the future. [ABSTRACT FROM AUTHOR]

The article examines the spatial migration of magmatic activity within the Caucasian segment of the Alpine Belt in the Early Neogene under the conditions of geotectonic setting. It discusses two basic assumptions on the origin of intraplate magmatism within Eastern Anatolia and the Caucasus. It presents the results of the isotope-geochronological investigation of some magmatic rocks of Southern Armenia and Eastern Anatolia. The article also cites the results of K-Ar dating of magmatic rocks of the Lesser Caucasus.

Results of the isotope-geochronological studies of the Late Cenozoic magmatism of Caucasus have been considered. The Neogene-Quaternary volcanic activity is found to have evolved during the last 15 m. y. being most intensive in the Middle-Late Pliocene. Within separate neovolcanic areas of the Caucasus region, magmatism was of a clearly discrete character when intense eruption periods interchanged with prolonged (up to several million years) times of quiet conditions. Four stages of young magmatism of the Caucasus are recognized: the Middle Miocene (15-13 Ma), the Late Miocene (9-5 Ma), the Pliocene (4.5-1.6 Ma), and the Quaternary (less than 1.5 Ma). However, for certain areas the time limits of these stages were shifted relative to each other and overlap the whole age range from the mid-Miocene to the end of the Quaternary period. Therefore, within the collision zone, the Neogene-Quaternary magmatism evolved almost continuously during almost the last 9 m. y., but in the time interval of 13-9 Ma in the Caucasian segment, volcanic activity was possibly low. No evidence of directed lateral migration of volcanic activity within the entire Caucasus region was found. At the same time, in the Lesser Caucasus the young magmatism commenced earlier (∼15 Ma), compared to the Greater Caucasus (∼8 Ma). [ABSTRACT FROM AUTHOR]