NEW DATA ON THE ISOTOPIC COMPOSITION (δ13С, δD, δ18O, 87Rb/86Sr AND 87Sr/86Sr) OF THE SIBERIAN PLATFORM BRINES

• Published in: Izvestiya Tomskogo Politekhnicheskogo Universiteta Inziniring Georesursov
• Main Authors: Dmitry A. Novikov, Aleksandr N. Pyrayev, Anatoliy V. Chernykh, Fedor F. Dultsev, Alexander V. Ilyin, Evgeny O. Chertovskikh
• Format: Article in Journal/Newspaper
• Language: Russian
• Published: Tomsk Polytechnic University 2021
• Subjects: brines; stable isotope composition 13c; 18o; d; isotopic ratios 87sr86/sr and 87rb/86sr; water–rock interaction; methanogenesis; smt processes; siberian platform; arctic; Engineering geology. Rock mechanics. Soil mechanics. Underground construction; TA703-712; Arctic
• Online Access: https://doi.org/10.18799/24131830/2021/7/3260; https://doaj.org/article/bb1b3ec71fd0409aaf1e98d659998c74

The relevance of the study is caused by obtaining new isotope-geochemical data for the Siberian platform brines. The aim of the research is to reveal the genesis of the brines and dissolved inorganic carbon as well as investigation of the water–environment interactions. Methods. Field sampling was carried out using common methods. Chemical analysis of brines was consist of titrimetry, ion chromatography and inductively coupled plasma mass spectrometry. The analysis of the stable isotope composition (δD, δ18O, and δ13С) was carried out using the Isotope Ratio Mass Spectrometer Finnigan TM MAT 253 equipped with H/Device (for δD analysis) and GasBench II (for δ18O and δ13СDIC analysis). The 87Sr86/Sr and 87Rb/86Sr isotope ratios were studied using the MI 1201T mass spectrometer in a two-strip mode with registration on one collector. Results. The new isotope-geochemical data on the Siberian platform supersaturated brines of a wide stratigraphic range (from Riphean to Ordovician) are presented. There is a wide range of oxygen and hydrogen stable isotope composition in the studied brines: from –133 to –17,5 ‰ for δD and from –17,0 to –2,5 ‰ for δ18O. The δD and δ18O values point on the sedimentation-metamorphic genesis of the brines. The carbon isotope composition of the DIC in brines range from –31 to +12,7 ‰. It is supposed that DIC has the biogenic (bacterial) origin. The youngest brine DIC has the heaviest carbon isotope composition whereas the oldest brine DIC has the biggest concentration of 12C. The strontium ratios of the studied brines divide them into two groups: with 87Sr/86Sr ratios, close to those of the modern ocean waters, and brines with 87Sr/86Sr values significantly exceeding modern ocean strontium ratios. It is assumed that the burial of the brines of the second group took place in the presence of clastic material of the continental crust, with a high content of radioactive 87Rb.