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Multi-isotopes (Sr-Nd-Pb-O-B) as indicators genesis of basaltic-andesitic ignimbrites and influence of meteoric-hydrothermal system at Verkhneavachinskaya caldera, Kamchatka

Olga V. Bergal-Kuvikas1,2,3 , Andrey V. Chugaev3, Sergey Dril4, Alexey N. Rogozin1, Kseniya A. Vialichka5, Ilya N. Bindeman5, Ivan P. Savov6, Samuele Agostini7

  • Affiliations:  1Institute of Volcanology and Seismology FEB RUS, Petropavlovsk -Kamchatky, Russia; 2Vitus Bering Kamchatka State University, Petropavlovsk-Kamchatsky, Russia; 3Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Moscow, Russia; 4Vinogradov Institute of Geochemistry SB RUS, Irkutsk, Russia; 5Department of Earth Sciences, University of Oregon, Eugene, USA; 6School of Earth and Environment, University of Leeds, Leeds, United Kindom; 7Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Pisa, Italy 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 85

  • Programme No: 3.16.12

  • Theme 3 > Session 16

Abstract

The present study aims to identify the conditions that led to the formation of the Late Miocene basaltic-andesitic ignimbrites at the Verkhneavachinskaya Caldera (VC), which extends over significant areas (120 km3, 10x12 km) on the Eastern Volcanic Belt, Kamchatka. New oxygen and hydrogen isotope data indicate that the intracaldera ignimbrites have low δ18O values, reaching -5.03‰ and - 182‰ δD values. The results obtained imply the presence of a substantial meteoric-hydrothermal system during the cooling of intracaldera pyroclastic flows in the presence of glacial meltwater, which subsequently led to the formation of the ignimbrite sequences of the VC. A comparison of Sr-Nd isotopes indicates the dominance of crustal evolution of the material, while Pb isotope systems suggest a significant contribution from slab fluid. Multi-isotope measurements allowed correlations to be revealed and the role of the meteoric-hydrothermal system to be ascertained.The present study aims to indentify whether elevated Pb-Sr isotope values could be associated with the introduction of these elements by potential sources from the radiogenic Cretaceous basement of Kamchatka. This would suggest a predominant role for the meteoric-hydrothermal system in the evolution of the geochemical characteristics of the VC ignimbrites. Conversely, variations in 143Nd/144Nd and their negative correlation with 87Sr/86Sr suggest a predominantly magmatic origin for at least some of the observed trends.The observed trend of δ11B with correlation to Nd isotopes suggests a substantial contribution of slab input to the magma explosivity of the VC.