GEOCHEMICAL OBSERVATIONS FROM FACTOR ANALYSES MAPS OF THE NATIONAL GEOCHEMICAL SURVEY DATABASE (NGS) AND OTHER DATABASES

In the USA, the federal government is the generator and data repository for the Regional Geochemical Mapping (RGM), and in some cases with state governments. Mineral Resources On-Line Spatial Data website is this vast RGM data repository, known as the National Geochemical Survey database (NGS). The objective of the present work is to process national and state data sets and to compare the results for important chemicals. Toward this end, using ArcMap IDW, geostatistical analyses that include factor analysis to reduce data to fewer and geochemically explainable variables were used. Interpolated maps of the factor score coefficients are developed. The results are interpreted in terms of their natural geochemical origin versus industrial or anthropogenic chemical families. Data from the 48/USA, New Mexico, and Colorado, are presented.

Chemicals heavily weighted or scored in one factor are easily or with difficulty identified with a geologic material or process, or both. Factors need to receive ascribable geologic names, or mixtures. Individual chemical concentration distribution maps are produced in order to compare elements in factors. In the present study, investigation of factors has proceeded beyond the previously suggested 5 factors, and significant information may be present with respect to accessory minerals. Observations are: 1) Mg responds from dolomites in sedimentary regimes; mafic rocks from igneous regimes; 2) Rare earth elements and Ti can be seen exiting the Appalachian Mtns as clastic material, resistates, and they are concentrated along the coast. 3) There is an agricultural factor within the greater Mid West. 4) Cr, V, Ni, Co, and Sc are indicators of mafic igneous rocks, and a mafic factor; Can Sc indicated mafic areas be subtracted from these other elements to indicate anthropogenically influenced regions?

Factors specifically are 1) A mafic igneous factor, which will often be weighted in Fe, Mg, Co,Ni, Cu and Cr, 2) An alkali felsic igneous factor will be mainly weighted as Na. K. Li, Be, Cs, F, REEs, 3) Clay has enrichments in Al and Ga, maybe with a little alkalis or alkali metals, and 4) Heavy REE factor, Light REE factor, or mixed. USA is compared with New Mexico and Colorado.