ИСТИНА

Geochemical methods of ore deposits exploration are widely used by geological surveys and mining companies for all stages of the exploration process. Many companies provides such operations and spends about 15% of their exploration budgets for this purposes. The constant interest to the geochemical methods is provided due to relatively low cost and high reliability of the results. More than 300 ore deposits, including the most famous polymetallic ones, were discovered with the use of geochemical prospecting. The rare earths elements (REE) are widely used in geology as markers. REE are members of group 3A and all have similar physical and chemical properties, but these elements may be partially separated by some petrological and mineralogical process due to variety and of the cation co-ordination polyhedra in rocks and minerals. The observed degree of REE fractionation can be a pointer to minerals and rocks genesis and, therefore, ratios of REE are important geochemical markers of ore bodies1. Compact systems for rapid determination of the mineral composition, based on Laser-Induced Breakdown Spectroscopy (LIBS), provides a unique opportunity to implement the requirements for routine analysis of geochemical samples: rapid, and low cost technique for a determination of a wide range of elements. But there are only few works on REE determination by LIBS due to significant spectral interferences between them and relatively low content in main geochemical material (soils, sediments and rocks). Therefore, the evaluation of sensitivity of the REE determination in rocks and soils by the LIBS is highly beneficial. This purpose requires improving the analytical capabilities of LIBS to analyze traces of metals in the geological samples. We estimate the limit of detection of light REE (yttrium, cerium, lanthanum, etc) in soils and rocks by LIBS with the use of 3s- criterion. We also estimated the limitation of LIBS determination of REE due to the spectral interferences with main components with the use of synthetic spectra calculated for LTE condition and sensitive to the spectral width of the slit, Doppler and Stark broadening.