Geochemical stream sediment signatures from Precambrian terrains of Uruguay

Abstract

Geochemical data of Uruguayan crystalline terrains collected in the 80’s were recovered by the National Mining and Geology Directorate of Uruguay (DINAMIGE) in 2020 involving 32,000 soil and stream sediment samples analyzed for 22 elements (Ag, As, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Nb, Ni, P, Pb, Sb, Sn, V, W, Y and Zn) by direct current plasma spectrometry. A set of 6755 samples of these data, more or less 21% of the total, were processed by multivariate statistical methods and geographic information system (GIS) procedures aiming characterization of geochemical signatures derived from environmental and geological processes. Samples were classified as background or anomalies/outliers at the beginning. The general data and the different sets were processed by statistical methods and GIS individually. The results considered the original units or sometimes, the transformed data for uniformity of variability. Nine geochemical signatures related to the geological domains were defined; three of them involved low contrast units with moderate enrichment in Ba, Co, Cu or Mn. The remaining six geochemical signatures were related to specific geological units and presented multivariate signatures. Seven signatures related to anomalies were defined, three of them of lithological origin, two superficial and the others mixed, including the possibility of sulphide deposits.