The thesis is dedicated to studying exogenic lithium salt halos. As a result of lithochemical investigations in the territory of Ukraine at above 40 proving grounds it was established that the exogenic lithium salt halos are formed in the surface deposits, independent of their composition and peculiarities. Certain regularity has been revealed in lithium total content distribution in the territory of the Ukrainian Shield its content decreases from the north-west to south-east that, in the author's opinion, is connected with the change of the soil type (from soddy podzolic soils to chernozem varieties) and, respectively with the change of clayey component. As to the distribution of mobile forms of lithium such regional regularity has not been established. The distribution of mobile forms of lithium in the USh territory reflects availability of potential geologic sources of lithium (lithium-enclosing rocks). It has been proved that the a correlation exists between lithium content in endogenic halo and that in exogenic salt halo. Thus it is possible to reveal deep-occuring lithium-enclosing rocks and ore displays of lithium by the exogenic lithium salt halos only. It has been established by results of thermodynamic calculations (temperature range from 2 to 45 °C at P = 0.1 MPa) of different types of soil dilutions and water at different pH values (from 3 to 9), that the basic form of lithium migration under salt halo formation is the cationic form - Li+ (99.9 %). This permits, with certain probability, using the salt lithium halos (which components exist as dissolved compounds or as those being in complicated relations with the rocks of solvable compounds) in geochemical researches. Parametric and nonparametric characteristics of exogenic salt lithium halos: the background and anomalous content of lithium and other chemical elements, lithium gamma, degree of lithium mobility, elements association in the exogenic halo, the halo area and morphologic peculiarities, and possible genetic origin of lithium halos have been established. Main lithium associations with other chemical elements in the salt halos of natural and technogenic origin have been determined. Under availability of exogenic natural lithium halos the associations of chemical elements correspond to those of endogenic halos (e.g., on the Polokhivka plot the endogenic halos of petalite-enclosing rocks are represented by the following associations - Li, Rb, Cs, Be, Ta, Nb, Sn, F; the relation Li, Rb, Cs Be, F is most distinctly traced in exogenic halo, and Li, F under tectonic disturbance. It has been proved for the first time that exogenic salt lithium halos (side by side with other geochemical methods) may be used in geochemical prospecting of minerals and in finding territories of ecological risk. Key words: lithium, exogenic salt halos, technogenic halos, natural halos, prospecting aspects, ecological aspects, halo element associations.
