Morphological and Minor Element Fingerprinting for Source Identification of Placer Gold from the Vulture Mine Area

The Vulture Mine, with over 340,000 ounces of reported gold production, is a historically important mine in Arizona. Four samples of placer gold from the area around the mine were examined in regards to geochemistry and morphology. The geochemistry of the four samples showed a direct correlation between increasing placer gold purity and increasing distance between the inferred lode source and the sample locations; conversely, silver purity decreased with distance. This is consistent with the hypothesis that lode gold shed into a placer will increase in gold purity as it travels further from its source, as silver in the alloy is preferentially weathered away. An in-depth look at the morphology of the placer grains revealed that samples found closer to the lode source had increasingly more grains which displayed sub-rounded and rounded shapes. This information supports the hypothesis that this placer gold came from the same gold lode source, and became more rounded as it traveled further from the source. This study suggests that placer gold chemistry and morphology may be a useful prospecting tool for tracing placer gold in specific streams back to the lode source. This could have large economic implications for the area surrounding the Vulture Mine, as future similar work may identify additional lode sources