Diagnóstico e caracterização das concentrações de elementos de terras-raras (ETR) na região central do escudo Sul-Rio-Grandense, estado do Rio Grande do Sul

Abstract

The substantial growth in the use of rare earth elements (REE), for applications in high technologies, ranging from the manufacture of supermagnetos and superconductors, electronics components and development of new materials has led to a significant increase in its demand across the world and in particular in Brazil, where the research and exploitation of these elements came to be cited as priority and strategic. Despite the rare earth elements may be present in more than 250 known mineral species, only in a few occurs in some concentration sufficient to justify their exploitation. In this sense, this paper conducted a data collection and compilation of geochemical analysis, in the region of central Shield South-Rio-Grande, placing greater emphasis in the municipalities of Caçapava do Sul,, Vila Nova do Sul and Lavras do Sul, strategically chosen for having historical mineralization of some metals. Besides having a great lithological diversity. It was consolidated a database consisting of 166 samples containing REE geochemical analyzes (trace). Being a part of this data available in bibliographies and other provided by researchers jobs that will be published. With the database was made a basic statistics for each of the 16 elements where was noted a positive correlation between the ETR and the silica content for some variables, making it interesting to divide the database in two distinct areas with different ranges of silica concentration. In the realization of the estimation using 3 classic interpolation methods (Distance Square Inverse, Modified Shepard and Minimum Curvature), the Modified Shepard method proved to be the best interpolation for the field of acid rocks, while the Minimum Curvature demonstrated to be the best for the field of intermediate and basic rocks. The choice of the best method was able to be identified through the use of cross-validation technique. With average grades of each ETR generated by the estimated data, it was possible to make a comparison with the deposits grades of know deposits in Brazil and the World. It is concluded that the grades of the two rock domains demonstrated to be much lower than the grades prevailing in economically viable deposits, since currently doesn’t exist sufficient technology to explore these grades as economically.