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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.

New data are presented on the quartz porphyry dikes of the Salmi batholith belonging to anorthosite–rapakivi granite rock complexes. The relationships of various igneous rocks of the Salmi batholith and metasomatites were determined along with the isotopic U–Pb age by the LA–ICP–MS technique and the temperature of zircon formation by the Ti content.

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.

Study of epochs of tectonomagmatic activity of the Earth in different parts of the planet and under various geodynamic environments suggests as one of the main tasks of such investigations establishment of their age, duration, evolution dynamics, spatial–age regularities of volcanic focus migration, and other characteristics allowing one to reconstruct the history of magma gen� esis for concrete regions on the level of individual time lags of the geochronological scale. In this paper we discuss the results of the study of geochronology of Miocene volcanism in the northern part of neovolcanic province in the Lesser Caucasus, which allows us to determine the time of beginning and total duration of the Late Cenozoic epoch of tec� tonomagmatic activization in this sector of the Cauca� sian–Anatolian segment of the Alpine foldbelt. Products of the earliest impulses of Neogene– Quaternary volcanism within the northern end of the mountain system of the Lesser Caucasus, as is evident from the results of geological and stratigraphic investi� gations [1], are abundant in the upper reaches of the Kura River on its left bank, where they form the exten� sive (60 × 30 km) Erusheti volcanic highland on the territory of Georgia and Turkey (Fig. 1). They are united in the Goderdzi Formation in the Georgian part of the region. The lower parts of sections of the formation are composed of the pyroclastic series with a thickness of up to 700 m represented by welded and loose layered tuff, breccia, and agglutinate, in which thin lava flows of dacitic or more basic composition are sometimes observed. Numerous volcanic edifices (Gumbati, Shalosheti, Digra, and others) significantly destroyed and smoothed by erosion, their dacite lava flows forming a sheet with a thickness of up to several hundred meters, and overlying pyroclastic formations on most of the region are located on the surface of the Erusheti highland. The maximal heights within the highland reach 3000 m (on the territory of Turkey); its basement is entirely composed of sedimentary and volcanogenic series of Eocene age. Effusive rocks of the Goderdzi Suite in the east in valleys of the Kura River and its right tributary Paravani are overlain by mainly basic Pliocene lavas of the Dzhavakheti high� land (3.7–1.6 Ma [2]) and further, in the latitudinal direction most likely entirely thin out in sections within the area of western ends of the Samsari ridge, where Quaternary lavas occur directly on rocks of the Early Cenozoic–Mesozoic basement [3]. The available concepts on the age of rocks of the Goderdzi Formation were mainly based on the results of investigations of plant and fossil remains in horizons of diatomic clays, which are known and were previ� ously mined in some locations at the bottom of the young effusive series in the Erusheti Highland [1, 4]. These data allowed us to establish the possible age range of the formation of pyroclastic rocks and lavas of the formation as Late Miocene–Early Pliocene. !"# !"$ !"% !"" !"& $# $$ $% !"’ !"( !&) !&* !&! + , .

Forecast of possible scenarios of eruptive activityfor volcanic centers and individual volcanoes as well asthe type and character of their future eruptions is animportant aspect of investigations of modern (Quaternary) magmatism of the Earth. Prognostic reconstructions of this type are impossible without analysis oftendencies in the development of volcanic centers anddetermination of the main time characteristics ofmagmatic activity occurred inside them. The Northern Caucasus is the only region in European Russiawhere modern magmatism was manifested, althoughonly to a small extent. Magmatic activity in the Anthropogene occurred there exclusively within the Elbrusneovolcanic center in the southern part of which theElbrus, one of the largest Quaternary volcanoes of theNorthern Eurasia, was formed lesser than 250 ka [1–3].Quaternary volcanism of the Elbrus center started~950–900 ka [4] with eruptions of three lava volcanoes (Tyzyl, Tashlysyrt, and Syltran) located withinthe linear submeridional zone at the Baksan andMalka interfluves. The regular decrease of SiO

One of the well-known areas with youngest volcanism in the Lesser Caucasus is located in the vicinity of the Borzhomi City (central Georgia) famous by mineral water springs. This relatively small area hosts four volcanoes (Tsitelidabadzveli, Tsikhisdzhvari, Mukhera, and Sargavi), which yielded extended (from 2 to 13 km long) flows of andesite to, subordinate, basaltic andesite lavas (figure). In scientific works dedicated to different aspects of Neogene‐Quaternary magmatism of the Caucasus region, manifestations of basaltic andesite‐andesite volcanism in the examined part of the Lesser Caucasus mountainous system are usually united into the Bakuriani‐Borzhomi neovolcanic area [1 and others]. It is composed of Upper Cretaceous carbonate bands, Paleocene‐Lower Eocene terrigenous rocks of the Borzhomi series, and Middle Eocene‐Oligocene volcano-sedimentary sequences. Young lava flows a few tens of meters thick known in this area lie with stratigraphic and angular unconformities upon the Paleogene basement spreading over significant part of studied territory (Fig. 1). It should be noted that, according to the recent tectonic map of Georgia [2], magmatic activity in the Bakuriani‐Borhomi area was concentrated in the Adzharia‐Trialeti zone of the Lesser Caucasus fold system with volcanoes confined to the linear near-latitudinal Bakuriani abyssal fault zone at its intersection with the meridional Samsari Fault. Tsitelidabadzveli Volcano (2320 m) is located on the northern slope of the Trialeti Range 12 km south of Borzhomi. It represents an oval meridionally extended edifice up to 100 m high composed of pyroclastics (scoria, breccia, lapillis) with subordinate interbeds of dark gray and reddish lavas. Basaltic andesite lava flows erupted by this volcano fill a spacious depression 8 × 6 km in size and form the Dabadzveli Plateau, the surface of which is located at altitudes of 2100 to 1600 m and is slightly inclined in the northern direction toward the Kura River valley. Basaltic andesites of the Tsitelidabadzveli Volcano (samples YUG-156 from the volcano cone and YUG-157 from lavas of the Dabadzveli Plateau) represent massive to vesicular porphyric to subordinate aphyric rocks. Phenocrysts in porphyric varieties are dominated by plagioclase (labradorite) and clinopyroxene (augite) accompanied by subordinate orthopyroxene (hypersthene) and olivine. Tsikhisdzhvari Volcano (1818 m) is located 2.5 km

The products of volcanic activity from the Kutaisi area and Guria (western Georgia) were studied in terms of isotope geochronology to determine the age of rocks and to confirm their attribution to Cenozoic formations. The results obtained show that the erupted rocks in the Kutaisi area were formed during the three pulses of Mesozoic volcanic activity: the Bajocian, Kimmeridgian-Tithonian, and Turonian-Santonian. It was shown that no displays of Late Cenozoic volcanism occurred in this region of the western Georgia. Because of this, its inclusion into the Central Georgian neovolcanic province, earlier supposed, seems to be improper. By the data of isotope geochronology, Guria is the only region of western Georgia where volcanic activity occurred in post-Paleogene period. Two pulses of young volcanism were revealed: of about 15.5 and 9-7.5 My. The former was related to the introduction of syenite intrusion, and the latter, to subaqueous exudation of subalka- line Neogene lavas. All the outcrops of Neogene rocks we found and dated in Guria fit within the well-pro- nounced sublatitudinal linear band which probably represents the occurrence in the Middle Miocene of a local zone of extension appearing under conditions of total compression during the collision of the Eurasian and Ara- bian lithospheric plates.