DELINEATING GOLD AND SILVER DISTRIBUTION IN FELDSPAR, CARBONATE, BASTITE, AND VEINS OF HYDROTHERMALLY ALTERED ROCKS FROM THE HELEN ZONE IN THE COVE DEPOSIT, LANDER COUNTY, NEVADA

The Cove deposit located in the northern Fish Creek Mountains of Lander County, Nevada is well known for its Carlin style gold deposits. Mineralizing hydrothermal fluids entered this locality in several pulsing events, using faults and dikes as feeders into the area. Directly northwest of the Cove deposit is the Helen Zone deposit, where mineralization is present in decarbonized dolostone within the Triassic Home Station Member of the Augusta Mountain Formation, decalcified limestone of the Favret Formation, and altered igneous mafic dikes.

Microscopy and Environmental Scanning Electron Microscope (ESEM) were used to analyze specific grains, veins, and veinlets within polished thin sections. This was done to delineate gold and silver distribution present in veins and veinlets of carbonates, as well as chemistry of carbonates, feldspars, and bastites. An Energy-Dispersive X-Ray Spectroscopy (EDAX) detector attached to the ESEM was used to collect weight percent data (ZAF corrected) of major and minor elements. Photomicrographs were taken of the areas in order to correlate them with ESEM scan lines. Preliminary scans on core sample AX16-1921 have defined major chemical variation in veins and the carbonate and silicate minerals. Precious metal concentrations are elevated in selective carbonate and sulfide veins and below detection levels in others. Altered ferro-magnesian silicates show detectable levels of gold (1.0 - 3.0 wt.%) and silver(0.3 - 1.5 wt.%) while crosscutting carbonate veins only have elevated levels of silver (0.3 - 1.0 wt.%).