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Humates and fulvates of uranium and thorium representing a form of actinide transfer in the environment have been investigated thoroughly enough. Nevertheless, formation of humates (fulvates) of radiogenic nuclides after the preceding high-energy act of nuclear recoil is studied quite insufficiently. This is because isotope 234U assimilated by humus alongside with isotope 238U in ancient biogenic rocks, e.g. black shales, is completely decomposed, while uranium-234 present in these rocks now has formed mainly during the last 1.5-2 million years. The question is: do radiogenic uranium and also other radiogenic nuclides of the uranium-238 series preserve the chemical form of humates (fulvates) in the solid organic phase of humus? Such a question is quite natural: as a result of alpha decay radiogenic atoms (or their nearest parent nuclides) obtain kinetic energy of recoil of the order of 105 eV, which leads to full or partial destruction of both the initial molecule and the neighbouring ones in the track of the recoil atom. The possibility to maintain (or reconstruct) humate (fulvate) complexes of radiogenic atoms in the solid phase after the act of nuclear recoil is not obvious. In the present work, graptolitic argillite (Dictyonema shale) taken from the core of borehole 191-a at a deposit in North-West Estonia was investigated. The sample 2304 was taken from the bottom quarter of the layer, approximately 75 (± 15) cm above its bottom. Alpha-ray spectrometric analysis data of the sample in question show the following activity ratios (AR) in the investigated sample: 234U/238U = 1.03 ± 0.02 and 230Th/234U = 0.99 ± 0.06, the average uranium content being ∼100 µg/g. These values suggest that uranium and its decomposition products present in the shale are in the state of radioactive equilibrium or rather close to it. In the investigated sample, the total content of organic carbon (by Tjurin method) and fraction and group composition of humus (by Plotnikov-Ponomarjov method) were determined. It was established that the shale sample contains 14.4% organic carbon, but only 0.26% of this amount (i.e. 0.018% of the total organic matter of shale) is related to humic and fulvic acids, in other words to humus acids themselves. The rest of organic matter (98.2%) is presented by humins insoluble in the conditions of standard analysis, and also by individual substances oxidizing with difficulty, which represent components of kerogen organic matter. Humus acids are presented by three fractions of humic acids and four fractions of fulvic acids. In humic and fulvic acids 238U and 234U content was determined. The influence of decalcination of humates and fulvates on isotopic composition of uranium was studied. After triple extractions, more than 30% of uranium present in shale is transferred into alkaline solutions. Its distribution is as follows: 20.2% in humic acids and 10.56% in fulvic ones. This sedimentation is not attributable to adsorption, occlusion or any other mechanism of uranium capture from a solution as proved by differing isotopic composition of uranium in the separated fractions. Uranium transfer into the deposit definitely proves the formation of chemical compounds of uranium with corresponding ligands in the humus phase of Dictyonema shale. The presence of radiogenic uranium in humic acids proves that, despite of significant destruction of organic matter in the track of the recoil atom, not only the molecule of humic acid is recreated from fragments and radicals, but also strong links of uranium-234 with both humic acids and fulvic acids form.… [ABSTRACT FROM AUTHOR]