The Castle Mountain prospect is a low sulfidation epithermal gold target with strong surface alteration. A paleo hot spring vent crops out at the top of Castle Mountain evidenced by a small area of sinter and silicified volcaniclastic rocks that carry anomalous gold. The surrounding area features strong argillic alteration with minor quartz stock-work veins.
Surface mineralization is hosted dense welded andesite breccia (mapped as debris flow breccia) having a maximum thickness of 170 meters. A lens of Paleozoic debris is interstratified with the andesite breccia. Below that, Tertiary andesite, ash flow tuff and a basal conglomerate sit unconformably on Paleozoic sediments. The estimated depth to the unconformity, based on a NBMG section drawn 2 miles to the southwest, is between 250m and 350m. This unconformity represents an excellent stratigraphic target for mineralization below the hot springs vent.
The Gravel Creek project in northern Elko County is the best analog for Castle Mountain. Gravel Creek is a new gold/silver discovery by Western Exploration. They have intercepts up to 16 meters long at 49 g/t Au, or up to 318 meters at 1.27 g/t Au. Mineralization at Gravel Creek there is hosted in silicified breccia formed at the basement/Miocene interface below a surface sinter and weak geochemical anomalies (Christensen, 2015). The host rocks at Castle Mountain are of similar age and lithology.