RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 6, NO. 4, PAGES 251–255, doi:10.2205/2004ES000161, 2004

The Elbrus Caldera in the Northern Caucasus: Geological structure and time of formation

Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM), Russian Academy of Sciences, Moscow, Russia

I. V. Melekestsev

Institute of Volcanic Geology and Geochemistry, Far East Division, Russian Academy of Sciences, Petropavlovsk-Kamchatski, Russia

P. W. Lipman, J. B. Lowenstern, and D. R. Miller

Geological Survey USA, Menlo Park, USA

Abstract

[1]  Complex field work in combination with the detailed interpretation of aerial and satellite photographs allowed us to discovered for the first time a large collapsed Elbrus Caldera (17 14 km along the edge of outer escarpment with a total area of ~230 km² ). The Elbrus Volcano is located in its southern part. The mass ejecta of rhyodacitic and rhyolitic pyroclastics and the formation of the tuff and ignimbrite coves are related to the caldera formation. Time of the caldera origin, according U-Pb (SHRIMP) dating on zircon from fiamme of ignimbrites is between 689 30-722 15 Ka. Based on comprehensive investigation of the rocks of the Elbrus volcanic center, including K-Ar, ³⁹Ar/⁴⁰Ar and EPR dating of rock-forming quartz, we identified in its evolution precaldera, caldera and postcaldera cycles. Two last cycles were subdivided into early and late stages.

Received 24 August 2004; published 7 October 2004.

Keywords: Elbrus Caldera, geological structure, time of formation.