Biogeochemical methods for prospecting
BIOGEOCHEMICAL METHODS FOR PROSPECTING (EN: Biogeochemical search; DE: biogeochemisches Suchen; FR: prospection biogeochimique; ES: prospeccion biogeoquimica; RU: биогеохимические поиски) are based on the study of the anomalous concentrations of the chemical elements within the various products of biosphere, or on the study of the reaction of organisms onto the impact of the chemical elements of the environment, for the identification of the deposits with useful minerals.
They have been proposed for the first time during the end of the 1920-ies by V. I. Vernadsky, and have been used within the USSR during the 1938 (S. M. Tkalich), and during the 1939 within Sweden (K. Burdnin). Depending on the type of the living matter, they distinguish the phyto-geochemical, peat-geochemical, zoo-geochemical, and soil methods for prospecting. The phyto-geochemical (phyto-metallometric) methods for prospecting are based on the determination of the contents of the chemical elements within the ash of the grassy, bushy, and woody plants. During the peat-geochemical methods for prospecting, they use the results from the analysis of the peats and swamp waters, during the zoo-geochemical methods for prospecting, they use the analyzes of the substances, which have been caused by the living activities of animals, and also the results from the studies of the various animal organisms. At the base of the soil method, there lays the determination for the content of the chemical elements within the humus layer, or the study for the specific types and forms of the micro-organisms within the soil.
The usage of the biogeochemical method for prospecting is effective at the swamps and peat bogs, where the obtainment of the lithochemical samples is difficult, and also under the conditions of the buried or leached lithogeochemical halos of dispersion, with the thickness of the allochthonous (brought from the far places) deposits of 5-20 metres. The samples are being obtained along the profiles, which are oriented across the strike of the predicted ore structures. The masses of the samples are determined by the requirements of the spectral and other analyses for the weighted quantities of ash. The interpretation of the results from the biogeochemical method for prospecting is conducted with taking into account the types for existence of the elements within the ores and halos, the character for the contact of the lithic and hydrochemical halos with the roots of the plants, the existence of the physiological barriers for absorption within the plants (in relation to the high concentrations of the elements within the soils), and the extents of mineralization. The biochemical abnormalities, which have been identified, and which are promising because of the ore, are verified with other methods for prospecting (geophysical ones, drilling, and so on). The biogeochemical methods for prospecting are most effective during the conducting of the small-scale and medium-scale prospecting works, in combination with the geo-botanical methods for prospecting, during which there are being examined the biological reactions of the plants onto the changes in concentrations of elements within the environment, and also in combination with other geochemical methods for prospecting and exploration.
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