GEOLOGICAL, HYDROGEOCHEMICAL, AND MICROBIOLOGICAL CHARACTERISTICS OF THE “OIL SITE” OF THE UZON CALDERA (Kamchatka)
N.L. Dobretsov1,2, E.V. Lazareva3, S.M. Zhmodik3,2, A.V. Bryanskaya4, V.V. Morozova5, N.V. Tikunova5, S.E. Peltek4, G.A. Karpov6, O.P. Taran7, O.L. Ogorodnikova7, I.S. Kirichenko3, A.S. Rozanov4, I.V. Babkin5, O.V. Shuvaeva8, E.P. Chebykin9
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4Institute of Cytology and Genetics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrentyeva 10, Novosibirsk, 630090, Russia
5Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrentyeva 8, Novosibirsk, 630090, Russia
6Institute of Volcanology and Seismology, Far East Branch, Russian Academy of Sciences, Piip blvd. 9, Petropavlovsk-Kamchatskii, 683000, Russia
7Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrentyeva 5, Novosibirsk, 630090, Russia
8Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrentyeva 3, Novosibirsk, 630090, Russia
9Limnological Institute, Siberian Branch, Russian Academy of Sciences, ul. Ulan-Batorskaya 3, Irkutsk, 664033, Russia
Keywords: Hydrothermal oil, Uzon caldera, hydrogeochemistry, Archaea, Kamchatka
Abstract
This study used geological, geochemical, and microbiological data to examine the Uzon oils and conditions within the Uzon caldera. The trace-element compositions of crude oils and solutions from boreholes and hydrothermal springs were determined by ICP MS. The majority of hydrothermal manifestations within the Uzon caldera are controlled by three trends of faults. The major fault zone, trending nearly E-W is located between Kikhpinych and Taunshits volcanoes. It acts as a magma conduit and hosts numerous oval-shaped hydrothermal vents. The oil site is situated on the periphery of the hottest area of highest hydrothermal activity within the Eastern thermal field. On the Eh-pH diagram, most solutions of the Uzon caldera define distinct fields and trends which correlate with the stability fields for sulfur and iron. The oil site is characterized by very wide variations in temperature and Eh-pH parameters of pore solutions. The geochemical signatures of the solutions at this site are broadly similar to those from other areas of the Uzon caldera but differ in their sulfide ion and sulfate ion concentrations. These differences can be explained by mixing of deep chloride-sodium hydrothermal solutions and solutions produced during surface oxidation of sulfide-containing material. With respect to the average continental crust, the Uzon oil is enriched in S, As, and Hg. The crude oil and solutions have broadly similar concentrations of B, S, Cl, As, Se, Br, Cd, I, Hg, and Pb and highly variable concentrations of Ti, V, Cr, Co, Ni, Cu, Cd, Nb, and Sn. The community structure of archaeal assemblages in springs and test pits at the Eastern thermal field was analyzed by 16S rRNA library and pyrosequencing methods. It was found that the proportion of archaea in the microbial communities of the Uzon caldera ranges from 2 to over 70% of the total sequences identified. Crenarchaeota were found in large proportions in all samples except one. The majority of the sequences in four samples were affiliated with Euryarchaeota, which comprise methanogenic archaea, extreme halophiles, and some extreme thermophiles. The results of geological, mineralogical-geochemical, microbiological and physicochemical studies of oil seeps in the Uzon caldera reveal distinctive geochemical characteristics of crude oil and the complexity of oil formation.
DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.003
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