REGIONAL GEOCHEMICAL MAPPING OF NEW MEXICO, USA: NATURAL AND ANTHROPOGENIC IMPLICATIONS

The spatial analysis of regional geochemical data has several environmental and geological applications. The environmental evaluation presented in this study is based on chemical analyses of stream sediments from the National Uranium Resource Evaluation (NURE) data set. The statewide database consists of 27,798 stream sediment sites. Twenty-four elements are selected which are Al, Ba, Ca, Ce, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Na, Nb, Ni, Pb, Sc, Sr, Th, Ti, U, V, and Zn. Univariate, bivariate, and multivariate statistics and GIS techniques are applied to classify the elements and to identify geochemical signatures, either natural or anthropogenic, with the purpose of finding their sources. The elements are spatially analyzed by mapping their concentration distributions, anomalous element locations, and the factor scores that resulted, and these features are integrated as modified GIS theme layers, which are then compared with geologic maps, hydrologic basins, and mining districts maps. The study concludes that (1) the distribution of the elements in stream sediments shows that most of the variability is controlled by the bedrock chemistry, (2) Anthropogenic sources have local influence in the geochemistry of the stream sediments., (3) The mafic factor consists of Co, Cr, Cu, Fe, Ni, Sc, Ti, V and Zn and it also clusters in the Rio Grande rift and Jemez lineament, (4) The REE factor consists of Ce, La and U, and it has strong, localized, clusters, (5) Mineral exploration and contamination assessment are definitely feasible with the use of the NURE data set and the statistical analyses performed in this study, 6) Background values of chemicals are presented for each drainage basin.