Paper No. 268-10
Presentation Time: 10:15 AM
TRACE ELEMENT ANALYSIS OF PLACER GOLD SAMPLES
Trace element analysis of placer gold can be used as a valuable exploration tool to determine the original deposit source and locate lode gold deposits. There are a number of elements which can, in various quantities, be present in placer gold particles. Native gold can be in complete solid solution with native silver and contain additional elements including Cu, As, Pb, Fe, and S. There is a reoccurring pattern of silver depletion along the rim of placer gold grains, which is observed in placer particles from New Mexico, Alaska, Arizona, and other deposits, whereas grains located at the original deposit source exhibit no such rim. Placer gold collected from multiple districts in New Mexico and Alaska, coupled with a broad database of previously analyzed placer gold samples indicate correlations between chemical signatures (especially gold, silver, and copper) and type of deposits (i.e., Au-rich copper porphyry deposits, Au porphyry deposits, skarns, and epithermal deposits). By completing a chemical analysis and determining the particle morphology of placer gold collected from these districts using an electron microprobe, patterns in the chemical signatures from each location can be used to examine chemical variability (1) within the individual placer gold particles, (2) within the same district and (3) among different districts.