The purpose of this study is to map the clay alteration across the northern portion of Barrick's Goldstrike property, located along the Carlin trend. The study focused on the occurrences of three specific occurrences, ammonium-illite, kandites, and changes in the AlOH feature position (broken into four classes: sodium-rich, slightly sodium-rich, normal, and iron-rich) along three section lines. The clay alteration was mapped using down-hole spectroscopy (a spectral measurement was collected at 5-20 ft depth intervals in each hole) and remote sensing (Probe-1 airborne sensor). The remote sensing portion utilized pixels extracted by averaging the spectra of ammonium-illites and illites showing different AlOH feature positions and individually running them through Spetral Angle Mapper and ratio codes to identify areas with ammonium-illite and changes in the AlOH feature position. Only ratio codes were needed to identify kandites in the remote sensing data.
The down-hole spectroscopy data of the ammonium-illite show that it occurred predominantly over a small gold deposit (Golden April), is strongly structurally controlled and is four times more abundant in ore-bearing holes than in non ore-bearing holes. Both types of remote sensing data showed the highest concentration of ammonium-illite occurred along section B-B'.
The down-hole spectroscopy data of the kandites showed a strong association to structures and felsic igneous material and that it is twice as abundant in ore-bearing holes than in non ore-bearing holes. The only concession is that both the gold deposits encountered in the section lines are partially hosted in igneous rock. The remote sensing data shows limited surface expressions and reiterates the structural control for kandite occurrence.
The down-hole spectroscopy data of the AlOH feature position shows a strong structural control and the strongest correlation to gold deposition. The sodium-rich and the slightly sodium-rich compositions are five and ten times more abundant in ore-bearing holes than in non-ore bearing holes, respectively. Remote sensing shows promise in being able to map changes in the AlOH feature position at the surface, but there is not a wavelength band on Probe-1 located completely within either the sodium-rich or slightly sodium-rich compositions.
All three of the occurrences mapped in this study show a correlation to gold and should be utilized as exploration tools in the future. The only concession to keep in mind is the fact that the ore encountered along the section lines is partially hosted in igneous material, which explains why kandites are twice as abundant in ore-bearing holes than in non ore-bearing holes. The AlOH feature position shows the strongest correlation to both gold deposits and would make the best exploration tool.