Techniques and Methods 11–C5
This report emphasizes geographic information system analysis and the display of data stored in the legacy U.S. Geological Survey National Geochemical Database for use in mineral resource investigations. Geochemical analyses of soils, stream sediments, and rocks that are archived in the National Geochemical Database provide an extensive data source for investigating geochemical anomalies. A study area in the Egan Range of east-central Nevada was used to develop a geographic information system analysis methodology for two different geochemical datasets involving detailed (Bureau of Land Management Wilderness) and reconnaissance-scale (National Uranium Resource Evaluation) investigations. ArcGIS was used to analyze and thematically map geochemical information at point locations. Watershed-boundary datasets served as a geographic reference to relate potentially anomalous sample sites with hydrologic unit codes at varying scales. The National Hydrography Dataset was analyzed with Hydrography Event Management and ArcGIS Utility Network Analyst tools to delineate potential sediment-sample provenance along a stream network. These tools can be used to track potential upstream-sediment-contributing areas to a sample site. This methodology identifies geochemically anomalous sample sites, watersheds, and streams that could help focus mineral resource investigations in the field.
First posted May 24, 2012
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Yager, D.B., Hofstra, A.H., and Granitto, Matthew, 2012, Analyzing legacy U.S. Geological Survey geochemical databases using GIS—Applications for a national mineral resource assessment: U.S. Geological Survey Techniques and Methods 11–C5, 28 p.
Data Sources and Methodology
Digital Mapping Methods
Symbolizing Raw Point Data
Establishing Geochemical Threshold Values
Thematic Mapping of Point-Geochemical Data
Thematic Mapping of Watershed Boundary Datasets Using Point-Geochemical Data
Hydrography Event Management Tools
Geologic Attributes of Anomalous National Hydrography Dataset Streams and Watershed Boundary Datasets
Geospatial Statistics of Point Data