ISOTOPIC RATIOS OF SULFUR (32S, 33S, 34S, 36S) IN ARCHAEAN ROCKS OF KARELIA - EVIDENCE OF MICROBIAL LIFE AND OXYGEN-FREE ATMOSPHERE
T.A. Velivetskaya, A.V. Ignatiev, S.V. Vysotskiy, A.V. Aseeva
Far Eastern Geological Institute, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok, Russia
Keywords: Isotopic ratios of sulfur, archean atmosphere, sedimentary sulfides, bacteria, Karelia
Abstract
Sulfur isotope ratios (33S/32S, 34S/32S, and 36S/32S) archived in the rocks of volcanic and ferruginous formations of the Sumozero-Kenozersky (~2.9 Ga) and Kostomuksha (~2.7 Ga) greenstone belts of the Fennoscandinavian shield were studied. The data obtained provide new arguments in favor of developing ideas about the existence of bacterial activity in the Archean ocean and the involvement of sulfur in the biogenic cycle, and also indicates the absence of free oxygen in the Earth’s Archean atmosphere. Based on the isotopic data of sulfur-34 and -33, the active activity of sulfate-reducing and disproportionating elemental sulfur bacteria in the surface environments of Archean sedimentary rocks was identified. The discovery of isotopic anomalies of sulfur-33 and -36 in the studied rocks became a key evidence of the absence of free oxygen in the atmosphere during the formation of the Meso- and Neo-Archean deposits of Karelia.
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