Abstract

The Gold Mountain mining district lies on the northeast flank of the Tushar Mountains, in northern Piute County of southwestern Utah. The mineralization in the Gold Mountain district was not discovered until prominent gold-bearing veins were located between elevations of 8000 and 10,600 feet in 1888 and the district was organized in 1889. Due to the rugged terrain, the mines are primarily accessed by a series of adits. District production is estimated at about 555,000 tons yielding 157,000 ounces of gold and 521,000 ounces of silver, or about 0.28 opt Au and 1 opt Ag recovered.

The Gold Mountain district is localized around the Kimberly quartz monzonite plug (about 24 Ma) that intrudes the coeval Oligocene-Miocene Bullion Canyon Group volcanic rocks just north of the Mount Belknap caldera. The Kimberly quartz monzonite is a medium-grained and equigranular to strongly porphyritic plug covering approximately 3 square miles. All of the rocks in the area are part of the Marysvale volcanic field.

There are two productive mines in the Gold Mountain district: the Annie Laurie on the east and the Sevier about a mile to the west. These two north-northwest-trending vein sets appear to outline a northwest-trending graben in the host quartz monzonite. The Annie Laurie vein trends about N. 20° W., 55° SW. and the Sevier trends roughly N. 15° W., 65° NE. The ore deposits are low-sulfidation, epithermal, white, quartz-carbonate ±adularia veins with minor fluorite and barite. The veins are primarily oxidized where they have been exploited. Ore minerals are rarely visible except for a little argentite and some fine native gold upon crushing and panning the ore.

A series of three exploration programs from 1981 to 1996 attempted to evaluate the remaining gold resources in the district, primarily at the Annie Laurie and Sevier mine areas. A total of 38 holes were drilled in these three programs. These exploration programs partially delineated two subeconomic resources: about 200,000 tons of 0.016 opt gold and 1.8 opt silver in the lower Kimberly mill tailings and a crudely estimated 100,000 tons of 0.15 opt Au and 1.5 opt Ag in the lower Annie Laurie mine.

While all of the past metal mining and documented exploration in the Gold Mountain district has been directed toward Au-Ag, other potential exploration targets may exist. The central area of pervasive argillic alteration in the Kimberly quartz monzonite (about 0.14 square mile) and the elevated Mo rock-chip anomalies (to 434 ppm Mo) could indicate a porphyry Mo (-Cu) system at depth.