VADOSE ZONE FLUID MIGRATION IN A HEAP-LEACH SITE USING TRANSIENT ELECTRICAL RESISTIVITY SURVEYS

Transient electrical resistivity surveys were performed at Cortez Gold Acres Facility, a heap-leach mine site, near Elko, NV to detect fluid flow through the unsaturated, heterogeneous crushed gold ore piles. The data collection system consisted of 36 surface electrodes and additional electrodes installed below the pile. Surveys were conducted along the top and sides of the pile with electrodes being placed over lysimeters installed beneath the pile. The resistivity data were calibrated against geochemical data and lysimeter data concurrently collected by University of Nevada, Reno researchers. This geophysical data was utilized to characterize and evaluate the current gold leaching practices to identify areas that were ineffectively leached. Areas with preferential flow paths and ineffective wetting were identified. This research proposes to expand on current knowledge of fluid recharge through heterogeneous, unsaturated zones and determine how effectively resistivity techniques can determine the timing of metals release during the leaching process.