Russian Journal of Earth Sciences
Vol. 6, No. 4, August 2004

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

A. G. Gurbanov1, O. A. Bogatikov1, I. V. Melekestsev2, P. W. Lipman3, J. B. Lowenstern3, D. R. Miller3, and A. Ya. Dokuchaev1

1Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM), Russian Academy of Sciences, Moscow, Russia
2Institute of Volcanic Geology and Geochemistry, Far East Division, Russian Academy of Sciences, Petropavlovsk-Kamchatski, Russia
3Geological Survey USA, Menlo Park, CA94024, USA


Abstract

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 times 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 pm 30-722 pm 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.