Content of rare-earth elements in the peat deposit of the high bog in the valley of the Dubches River (Krasnoyarsk krai)
L.V. KARPENKO
Federal Research Center “Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences”, Krasnoyarsk, Russia
Keywords: lanthanides, main input sources of rare earth elements, peat profile, clarke, reconstruction, Holocene
Abstract
A study was made of the gross content of rare-earth elements (scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, tulium, ytterbium and lutetium) in the peat deposit of the high bog in the Dubches River valley (Krasnoyarsk krai). It was revealed that the age of the bottom peat layer is 13 617 ± 190 cal BP. The main sources of rare-earth elements entering the peat deposit of the bog are considered. They are underlying rocks, atmospheric aerosols, regional and local forest fires, and peat geochemistry. It was noted that atmospheric aerosols and regional forest fires had little effect on the concentration of elements in the peat studied. The main sources of input of rare-earth elements into the peat deposit were the underlying rocks and the oxide-recovery environment at the initial period of the formation of the bog. During the study it was found that the content of rare-earth elements in the upper, transitional and lowland peats is below the clarke number and all the elements are dispersed. Cerium, terbium, and holmium are most dispersed in the upper and transitional types of peat, and cerium and terbium in the lowland ones. The concentrations of scandium and ytterbium in the lowland peat types are close to the soil clarke. It is concluded that the concentration of rare-earth elements in different types of highland and transitional peats down the profile not almost change. Their insignificant accumulation is noted only in the near-surface layers of 0.30-0.35 m. In pyrogenic interlayers at the depths of 2.65, 2.90, 3.15, and 3.25 m, increased content of almost all rare-earth elements relative to the overlying layer of peat was recorded. In the lowland types of peat in the depth interval of 4.0-3.75 m, the highest concentration of all elements was noted. It is suggested that the main source of rare-earth elements in the initial stage of bog development could be the bedrock of ancient glacial origin.
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