Kriging Hydrochemical Data
As a part of the National Uranium Resource Evaluation Program (NURE) water samples were collected from existing wells in all the continental United States. These samples were analyzed for some 30 elements and ions. Data were assembled for each 2 degrees RMTS quadrangle. The objectives of the NURE program included identification of areas favorable for exploration and producing estimates of recoverable resources. Other authors have reported on the use of pattern recognition, cluster analysis, and discriminant analysis to identify favorable areas.
In cooperation with the Uranium Resource Evaluation Group at Oakridge, the author utilized data from Plainview Quadrangle (Plainview, Texas) to examine the effectiveness of kriging to contour data on 13 variables including uranium. These variables were selected for their chemical association with the deposition or leaching of uranium salts. Because of strong dissimilarities between the Ogallala (Pliocene) and Permian groupings, the data were segregated.
Variograms were computed for each variable, separately for the Permian and Ogallala. Variogram models were cross-validated using randomly selected data subsets. In addition to kriged contour maps for the 13 variables and kriging variance maps in both the Permian and Ogallala, weighted linear sums also were considered. Two different weightings were considered, the weights were determined by a discriminant analysis model. Unusual regions were identified as those for which the kriging error exceeded two kriging standard deviations. These regions were correlated strongly with those identified by a discriminant analysis model and by the quadrangle evaluation.
KeywordsNatural Factor Variogram Model Untransformed Data Favorable Area Hydrogeochemical Data
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