Geologic description
In the late 1950s, Moneta Porcupine Company staked claims in the area but subsequently dropped them. William Huff and James Fucas continued prospecting in the area and staked several claims. Their claims were optioned by the Bunker Hill Mining Company in 1965. They dropped the claims at the end of the field season and the property was optioned by a succession of companies through 1981: Humble Oil and Refining Company, El Paso Natural Gas Company, and AMAX Exploration Inc. Sometime in the 1970s, a mine car and track were taken by helicopter to the prospect and an adit was started to intersect a silver vein. However, the adit extended only a few feet into the rock. About 20 feet of trenching was also done at that time. Still and others (2002) sampled the prospect during a Bureau of Land Management mineral assessment of the area.
The rocks in the prospect area are part of a belt of Mesozoic or Paleozoic sedimentary and volcanic rocks that have been metamorphosed to schist and gneiss. The belt is about 1 1/2 mile wide and strikes northwest (Brew, 1997; George and Wyckoff, 1973). The metamorphic rocks are bounded on the east by a thick, regionally extensive, 60 to 70 Ma tonalite sill and on the west by a 90 Ma granodiorite pluton (Brew, 1997 Still and others, 2002). On the north side of Groundhog Basin about a mile northwest of this prospect, the metamorphic rocks are intruded by a 16.3 Ma biotite 'tin' granite pluton. The granite is probably the source of the numerous rhyolite dikes and sills that extend from it and the mineralization in the area (Newberry and Brew, 1989). The mineralization at the North Silver Whistlepig Adit prospect consists of narrow, argentiferous, galena-bearing quartz veins (Still and others, 2002). The veins are from 0.2 to 1.0 foot thick, pinch and swell, and are exposed for about 50 feet in the steep rock face above a short adit that only extends a few feet into rock and does not intersect the veins. Several samples of the vein material collected by Still and others (2002) contained from less that 5 to 4,345 parts per billion gold, 11.5 parts per million (ppm) to 517.62 ounces of silver per ton, 778 ppm to 39.75 percent lead, 377 ppm to 11.0 percent zinc, and 17 to 1,497 ppm tin. Gneiss at the adit contains small vugs of quartz and fluorite; a sample across 3.6 feet of the gneiss contained 954 ppm lead, 399 ppm zinc, and 11.9 ppm silver. |
