At the Lisbon Valley Mining Company (SE Utah), exploration for sedimentary-hosted copper deposits has used both conventional soil sampling and sampling of ant hills for surface geochemistry. Anthill prospecting is a sampling technique that exploits the ants’ natural sorting ability as they transport material from the subsurface. The data sets for each of these techniques can be compared using Geographic Information Systems (GIS) to evaluate the effectiveness of each sampling technique. Surface geochemistry is a commonly used tool in the exploration for ore deposits. GIS is a useful program for visualizing spatial datasets, such as soil geochemistry, fluid geochemistry, stratigraphy, and fault locations. Exploration using GIS provides a preliminary assessment that can help find possible economic mineralization comparing different retrieval methods of soil data provided by the mining company.
The mine lies on the eastern portion of the Colorado Plateau region within the section overlying the Paradox Basin. Structurally, the mine sits in the collapsed flank of a salt anticline with ore trends following normal faults in the section above salt. Deeper faults likely provided conduits for copper-rich fluids derived from Pennsylvanian sediments. Current mining operations exploit hypogene chalcocite with lesser amounts of bornite and chalcopyrite in sandstones and conglomerates of the Cretaceous Burro Canyon Formation and Dakota Sandstone. In lower Lisbon Valley, economic mineralization thus shows both stratigraphic and structural control. The faulted flanks of the valley provide economic copper, and the faulted valley graben and wash plain provide footprints for fluid flow of copper ions through the system.
Exploration has started further southeast from the mine along the faulted margins of the valley. Soil and anthill samples in the exploration areas were analyzed by ICP-MS, and concentrations were plotted by editing symbology. Similarities between the anthill and soil samples were identified. All sampling techniques revealed higher concentrations of copper proximal to the major normal faults associated with salt-anticline collapse, and the extension of structural control. This was as expected observing the current mining trend within the valley. The high copper concentrations near faults are consistent with the hypothesis that faults controlled flow of fluids that made ore deposits possible. Spatial analyses maps based off conversion of bulk composition to point data illustrates prospects in Lower Lisbon Valley as viable options for economic extraction of copper.
