WHOLE-ROCK GEOCHEMICAL CHARACTERISTICS OF THE BUTTON HILL GOLD DEPOSIT, ELKO COUNTY, NEVADA

The Button Hill deposit is a high-grade, sediment-rock-hosted, disseminated gold deposit located in northeastern Nevada, at the northern end of the Carlin Trend. Gold at Button Hill is hosted in hydrothermal, tectonic and collapse breccias, with areas of pervasive silicification, within the upper Bootstrap limestone and the overlying, highly deformed, siltstones of the Rodeo Creek formation.

Multiple hydrothermal events have altered much of the rock chemistry, or caused dilution of immobile elements. Positive identification of lithologies is challenging, particularly in rock chips, which makes mapping and determination of the controls on mineralization difficult.

A principal component analysis (PCA) of data generated from ICP-MS of 11,975 ft. (3,650 m) of reverse circulation (RC) chips from 12 drill-holes identified 4 suites of elements. Three of the suites are interpreted as representing the geochemical signature of mineralization (Au, Ag, As, Cu, Sb, Te, and W), pre-mineralization alteration (Ca, Mg, Mn, and S), and lithological variations (Al, Ce, La, Nb, and Ti). PCA results are consistent with Grant isocon plots of unaltered Rodeo Creek versus brecciated, gold-bearing Rodeo Creek that show enrichment in Au, Ag, As, Ba, Cu, Fe, Li, S, Sb, Se, Te, Tl, and W; depletion in Ca, Mg, Mn, Mo, Ni, Sc, Sr, V, and Zn; and fixed ratios of Al, Hf, K, La, Na, Sn, Ti, and Zr.

Fixed ratio ("immobile") elements may be useful for lithogeochemical characterization. There are statistically significant variations in lithogeochemistry across contacts. However, there is a large amount of overlap in the spread of the data from any unit that makes it difficult to utilize this information for mapping.

Subsurface geochemical profiles of gold and those elements found to be associated with mineralization show anomalous As, Tl, Te, S, Se, and W associated with significant concentrations of gold. In general, Ag and Sb are associated with Au, however, some zones with high concentration of Ag and/or Sb have been found to lack significant Au. Anomalous Cu often appears to be associated with Au, though highest concentrations are found in the "upper plate" rocks of the Vinini formation, with no apparent association to Au mineralization. Anomalous Ag, As, Tl, Te, W, and Sb may be the most useful pathfinder elements to focus efforts in near and far exploration.