Известия Томского политехнического университета: Инжиниринг георесурсов (Feb 2020)
HYDROCHEMICAL COMPOSITION AND RARE-EARTH ELEMENTS IN ICE WEDGE OF THE KARA REGION CRYOLITOZONE KEY AREAS
Abstract
Relevance of the research. Information on composition, ice content and geochemical characteristics of frozen rocks is necessary for exploration of oil and gas condensate fields of Yamal, Gydan and Taimyr. Among the factors determining the tundra landscapes ecology of the cryolithozone, underground ice and their melting have great importance. The hydrochemical composition and rare-earth elements content in syngenetic ice wedge retain the information on the moisture sources and conditions of their formation. The main ions correlation and rare-earth elements distribution in the ice composition can be used to estimate the influence of such natural factors as precipitation, sea and volcanic aerosols and anthropogenic pollution. The main aim of the research is to identify chemical elements sources and to assess the impact of the ice type on hydrochemical composition and rare-earth elements distribution in different genetic types of ice – wedge, seasonal and firn ice. Objects: ice wedge, sediments rocks, seasonal ice, surface water, taken in expeditions Earth Cryosphere Institute, Tyumen scientific centre SB RAS in 2009–2014. Methods of chemical research: inductively coupled plasma mass spectrometry, atomic absorption spectrometry, emission photometry, chromatography. Results. It is established that marine and continental aerosols influenced the chemical composition of ice wedge studied in the coastal zone of the key areas of Belyj island, Sibiryakova island, Western Yamal and Western Taimyr. Fresh and ultrafresh syngenetic ice wedge is formed by freezing melt water, which contains snow-sorbed sea aerosols – suspended in the atmosphere solid and liquid particles. Ice wedge in the lake Sokhonto area long-distanced from the sea has no signs of marine influence according to the main ions content. Ice wedge with mineral inclusions was formed not only due to snow melt water with aerosols of continental origin, but also due to the suprapermafrost water. It was found out that lanthanide content in water-soluble form has increased in comparison with both сlark values and the content in the modern surface ice. In the most of examined syngenetic ice wedge the participation of marine aerosols is confirmed taking into account the cerium anomaly. Moreover according to the distribution of rare-earth elements the correlation between light and heavy rare-earth elements typical for ice wedge, equal to 0,9, and correlation between lanthanum and the other lanthanides, equal to 0,2, are observed. Sea ice inherits the mineralization and composition of sea water. Lake ice varies in depth and reflects seasonal changes in hydrochemical composition of ice and increases in concentration of marine aerosols in the snow covering the lake ice. Firn ice of the polar Urals has a very low mineralization, there are no impurities of sea aerosol. The natural mechanism of rare earth elements accumulation in water-soluble form in combination with iron, thorium and yttrium is implemented in ice wedge of the Holocene and Neopleistocene. Melting out ice wedge may lead to the flow of rare-earth elements in the surface water.
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