Conceptual models in exploration geochemistry-The Basin and Range Province of the Western United States and Northern Mexico

This summary of geochemical exploration in the Basin and Range Province is another in the series of reviews of geochemical-exploration applications covering a large region; this series began in 1975 with a summary for the Canadian Cordillera and Canadian Shield, and was followed in 1976 by a similar summary for Scandinavia (Norden). Rather than adhering strictly to the type of conceptual models applied in those papers, we have made use of generalized landscape geochemistry models related to the nature of concealment of ore deposits. This study is part of a continuing effort to examine and evaluate geochemical-exploration practices in different areas of the world. Twenty case histories of the application of geochemical exploration in both district and regional settings illustrate recent developments in techniques and approaches. Along with other published reports these case histories, exemplifying generalized models of concealed deposits, provide data used to evaluate geochemical-exploration programs and specific sample media. Because blind deposits are increasingly sought in the Basin and Range Province, the use of new sample media or anomaly-enhancement techniques is a necessity. Analysis of vapors or gases emanating from blind deposits is a promising new technique. Certain fractions of stream sediments show anomalies that are weak or not detected in conventional minus 80-mesh fractions. Multi-element analysis of mineralized bedrock may show zoning patterns that indicate depth or direction of ore. Examples of the application of these and other, more conventional methods are indicated in the case histories. The final section of this paper contains a brief evaluation of the applications of all types of sample media to geochemical exploration in the arid environment of the Basin and Range Province. ?? 1978.