Geometry and Zircons U-Pb Geochronology of the Mtkvari Ignimbrites Flow, Samtske-Javakheti Volcanic Highland, Lesser Caucasus

Okrostsvaridze, Avtandil and Chung, Sun-Lin and Lin, Yu-Cin and Skhirtladze, Irakli (2017) Geometry and Zircons U-Pb Geochronology of the Mtkvari Ignimbrites Flow, Samtske-Javakheti Volcanic Highland, Lesser Caucasus. Bulletin of the Georgian National Academy of Sciences, 11 (4). pp. 82-89. ISSN 0132 - 1447

Geom. and U-Pb dating. Moam., 2017.pdf

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In the Samtskhe-Javakheti Volcanic highland (Lesser Caucasus), in the Mtkvari river canyona large volcanic pyroclastic flow outcrops, which is represented byignimbrites ofandesitic-dacitic composition.Despite the fact that one of the important monuments of Georgian cultural heritage cave-city Vardzia is hewn into this flow, the question of its geometry andgeochronologyis still unclear. Field works showed that the Mtkvariignimbrites flow traced continuously from the Karzametifortress to the Khertvisi fortress for more than 35 km.Thickness of the flow increases obviously from the magma centre (40 m on average) to the periphery (80 m on average),though its width isnot still defined.The flow is inclined to the northern direction by 2-4oangle. Perfectly straight surface of the flow and its bottom conforms to the relief,which confirms its magmatic formation. The flow is cut by a regionalfault the Mtkvaricanyon. At the same time, together with its enclosingrocksit is divided into smaller blocks by cuttinglocalfaults.In isotopic laboratory of the National Taiwan Universitythe zircons of this pyroclastic flowwere datedby U-Pb method, using LA-ICP–MSequipment. The samples were taken from three main parts of the flow: at the end of the flow, near the Khertvisifortress(at 35 km;#13Geo4), in the central part of the flow, near the Vardziacave-city (at 15 km;#13Geo5) and at the beginning of the flow, near the Karzametifortress(#13Geo6). The resultsare practically identical within the margin of error and correspond to the Upper Miocene epoch:#13Geo4=7.500.42 Ma; #13Geo5=7.540.21 Ma; #13Geo6 =7.520.21 Ma. These almost identical results ofthe U-Pb geochronology from various sections ofthe Mtkvarivolcanic flow indicate great credibility of this dating.

Item Type: Article
Subjects: Q Science > QE Geology
Depositing User: ავთანდილ ოქროსცვარიძე
Date Deposited: 10 Jan 2018 08:13
Last Modified: 10 Jan 2018 08:13

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