Chronology of Magmatic Activity and Petrologic–Mineralogical Characteristics of Lavas of Kazbek Quaternary Volcano, Greater Caucasus

Lebedev, V. A.; Parfenov, A. V.; Vashakidze, G. T.; Gabarashvili, Q. A.; Чернышев, И. В.; Togonidze, Manana

doi:10.1134/s086959111801006x

Cited by 8 publications

(4 citation statements)

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“…The Kazbegi samples lie near the Pliocene to Quaternary volcanic center of Mt. Kazbegi (Figure ; e.g., Lebedev et al, , , ), and magmatic activity could potentially affect low‐temperature thermochronometric ages here via hydrothermal convection or a local increase in the geothermal gradient (e.g., Ehlers, ; Peyton & Carrapa, ). Our thermal modeling of sample K1 predicts cooling prior to onset of magmatism in this region at ~5 Ma (Figure b), and Pliocene AHe ages have been reported in other parts of the Greater Caucasus away from Cenozoic volcanic centers, including in the Tsei valley ~60 km northwest of Mt.…”

Section: Discussionmentioning

confidence: 99%

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

et al. 2020

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Along the northern margin of the Arabia-Eurasia collision zone in the western Greater Caucasus, the Main Caucasus Thrust (MCT) juxtaposes Paleozoic crystalline basement to the north against Mesozoic metasedimentary and volcaniclastic rocks to the south. The MCT is commonly assumed to be the trace of an active plate-boundary scale structure that accommodates Arabia-Eurasia convergence, but field data supporting this interpretation are equivocal. Here we investigate the deformation history of the rocks juxtaposed across the MCT in Georgia using field observations, microstructural analysis, U-Pb and 40 Ar/ 39 Ar geochronology, and 40 Ar/ 39 Ar and (U-Th)/He thermochronology. Zircon U-Pb analyses show that Greater Caucasus crystalline rocks formed in the Early Paleozoic on the margin of Gondwana. Low-pressure/temperature amphibolite-facies metamorphism of these metasedimentary rocks and associated plutonism likely took place during Carboniferous accretion onto the Laurussian margin, as indicated by igneous and metamorphic zircon U-Pb ages of~330-310 Ma. 40 Ar/ 39 Ar ages of~190-135 Ma from muscovite in a greenschist-facies shear zone indicate that the MCT likely developed during Mesozoic inversion and/or rifting of the Caucasus Basin. A Mesozoic 40 Ar/ 39 Ar biotite age with release spectra indicating partial resetting and Cenozoic (<40 Ma) apatite and zircon (U-Th)/He ages imply at least~5-8 km of Greater Caucasus basement exhumation since~10 Ma in response to Arabia-Eurasia collision. Cenozoic reactivation of the MCT may have accommodated a fraction of this exhumation. However, Cenozoic zircon (U-Th)/He ages in both the hanging wall and footwall of the MCT require partitioning a substantial component of this deformation onto structures to the south. Plain Language Summary Collisions between continents cause deformation of the Earth's crustand the uplift of large mountain ranges like the Himalayas. Large faults often form to accommodate this deformation and may help bring rocks once buried at great depths up to the surface of the Earth. The Greater Caucasus Mountains form the northernmost part of a zone of deformation due to the ongoing collision between the Arabian and Eurasian continents. The Main Caucasus Thrust (MCT) is a fault juxtaposing old igneous and metamorphic (crystalline) rocks against younger rocks that has often been assumed to be a major means of accommodating Arabia-Eurasia collision. This study examines the history of rocks along the MCT with a combination of field work, study of microscopic deformation in rocks, and dating of rock formation and cooling. The crystalline rocks were added to the margins of present-day Eurasia about 330-310 million years ago, and the MCT first formed about 190-135 million years ago. The MCT is likely at most one of many structures accommodating present-day Arabia-Eurasia collision.

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Section: Discussionmentioning

confidence: 99%

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

et al. 2020

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“…1 The K-Ar dating of samples was carried out using a highly sensitive low-blank technique developed at the IGEM RAS to date young rocks. Its detailed description, including the geochemical principles, characteristics of mass-spectrometric equipment, the algorithm of analytical procedure, and the assessment of measurement accuracy were reported in (Chernyshev et al, 2006;Lebedev et al, 2018b). The groundmass of lavas and monomineral fraction of biotite were used as K-Ar geochronometer.…”

Section: Methodsmentioning

confidence: 99%

The Pliocene Post-Collisional Volcanism of Central Armenia: Isotope-Geochronology and Geochemical Evolution of Magmatic Melts

et al. 2021

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The paper presents the results of isotope-geochronological and petrological-geochemical study of young volcanic rocks in the Geghama highland (Central Armenia), which were formed at the Pliocene-Early Quaternary stage of the Late Cenozoic post-collisional magmatism of the Lesser Caucasus. The boundaries of the area of volcanic activity manifested during this stage were established. The total duration (3.5-1.9 Ma) of the Pliocene-Early Quaternary stage, the time range of its main phases, and the scale and nature of eruptions were determined. Petrological and geochemical data indicate that the studied young volcanic rocks from Central Armenia belong to the mildly alkaline series and are represented by a continuous association of (trachy-)basalt-mugearite-latite-trachyte-rhyolite. The geochemical evolution of parental basaltic melts was mainly controlled by the fractional crystallization with Cpx as the main cumulus phase. Crustal assimilation and mixing of magmas were of limited importance: their possible contribution was recorded only in the most silicic rocks. The deep source responsible for magma generation under the studied part of the Lesser Caucasus at the Pliocene-Pleistocene boundary was represented by the asthenospheric mantle that was enriched during previous long-term (tens of millions of years) subduction of the Neotethys slab. Melting occurred in the Grt-peridotite stability zone; the composition of derived melts was geochemically similar to E-MORB basalts. An important feature of the regional mantle source was the notable admixture of subduction component. The generalization of the obtained petrological-geochemical and isotope-geochemical data on the young igneous rocks formed at different stages of Late Cenozoic magmatism at the Geghama highland allowed us to trace the evolution of the main parameters (mineral, chemical, and isotopic composition, depth of location, degree of melting) of mantle reservoirs responsible for magma generation beneath Central Armenia at the post-collisional stage (from the Late Miocene to the Holocene).

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“…The northern boundary of the youngest volcanism passes along the sources of the Maili and Chachi glaciers, further along the valley of the Devdoraka River up to the Daryal Gorge and then cut through the Tergi River in Paleozoic granites. To the north-west, the territory of the Kazbeki center ends at the Suatisi glacier and the Dzhimara summit (Lebedev et al 2018). The Kazbeki Volcanic Field includes a Kazbeki (5033 m) stratovolcano located in the middle of the caldera of its predecessor, Paleo-Kazbeki (Dzotsenidze et al 1985;Koronovskii and Demina 2003;Lebedev et al 2014), and more than ten satellite volcanoes located from the east, south and west sides of the arc such as the Big Tkarsheti, Shevardeni and Kechuttsveri.…”

Section: Rudiments Of Local Geology and Locationmentioning

confidence: 99%

“…Available radiometric data together with the interpretation of detailed satellite images, the chemical composition of volcanic cones and their lava flows allowed to determine four main magmatic phases in the Kazbeki volcanic field: phase I: 460-380 ka; phase II: 310-200 ka; phase III: 130-90 ka and phase IV: less than 50 thousand years ago. In addition, within the specified periods of phases II and III, early and late stages are additionally distinguished (Lebedev et al 2018).…”

Section: Rudiments Of Local Geology and Locationmentioning

confidence: 99%

Magnetic dating of the Holocene monogenetic Tkarsheti volcano in the Kazbeki region (Great Caucasus)

Vashakidze

Goguitchaichvili

Redondo

et al. 2019

Earth Planets Space

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The radiocarbon technique is widely used to date Late Pleistocene and Holocene lava flows. The significant difference with palaeomagnetic methods is that the 14 C dating is performed on the organic matter carbonized by the rock formation or the paleosols found within or below the lava flow. On the contrary, the archaeomagnetic dating allows to date the moment when the lava is cooling down below the Curie temperatures. In the present study, we use the paleomagnetic dating to constrain the age of the Tkarsheti monogenetic volcano located within the Kazbeki Volcanic Province (Great Caucasus). A series of rock-magnetic experiments including the measurement of hysteresis curves, isothermal remanence, back-field and continuous thermomagnetic curves were applied. These experiments indicated that Pseudo-Single-Domain Ti-poor titanomagnetite is responsible for remanence. A characteristic remanent magnetization was obtained for all twenty analyzed samples yielding a stable single magnetization component observed upon both thermal and alternating field treatments. Comparison of the mean directions obtained (Inc = 48.6º, Dec = 6.4º, A 95 = 4.0° and K = 67) with the SCHA.DIF.14k model yielded two main time intervals (4740-4650 or 4427-4188 BC) as the best age estimate of the Lesser Tkarsheti lava flow. These results suggest an earlier age (between approximately 200 and 700 years) for this monogenetic lava flow than expected from the estimated age provided by a former 14 C dating obtained in 1973 on woody remains. This first attempt to use the archaeomagnetic technique in the Caucasus indicates that the SCHA.DIF.14k geomagnetic model may be successfully used for dating purposes in the region .

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Chronology of Magmatic Activity and Petrologic–Mineralogical Characteristics of Lavas of Kazbek Quaternary Volcano, Greater Caucasus

Cited by 8 publications

References 14 publications

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

Evolution of the Greater Caucasus Basement and Formation of the Main Caucasus Thrust, Georgia

The Pliocene Post-Collisional Volcanism of Central Armenia: Isotope-Geochronology and Geochemical Evolution of Magmatic Melts

Magnetic dating of the Holocene monogenetic Tkarsheti volcano in the Kazbeki region (Great Caucasus)

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