North Shepard

Occurrence, Active?

Commodities and mineralogy

Main commodities Au; Cu
Other commodities As; Co
Ore minerals arsenopyrite; chalcopyrite; gold
Gangue minerals quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale MD
Quadrangle map, 1:63,360-scale C-3
Latitude 63.6431
Longitude -154.3001
Nearby scientific data Find additional scientific data near this location
Location and accuracy The North Shepard occurrence is situated on the northeast-facing side of a ridge between Johns and Shepherd Creeks. The occurrence is located 0.3 mile northeast from the center of Section 30, T. 21 S., R. 24 E., of the Kateel River Meridian. The site is accurate to within 500 feet (152 m).

Geologic setting

Geologic description

The North Shepard occurrence consists of quartz veins contained in felsic dikes. Anomalous gold mineralization is associated with quartz-sericite alteration of the dikes (DiMarchi and others, 1992, Newmont Mining Corp., 2012). The quartz veins contain disseminated arsenopyrite, chalcopyrite, and carry gold values; they are found in zones of silicic and phyllic alteration in the quartz monzonite dikes.
Surface samples collected by DiMarchi and others (1992) contain up to 500 ppb gold. Nine samples averaged 100 ppb gold. Copper, cobalt, and arsenic values were not reported.
Newmont Mining Corporation (2012) collected soil samples and rock chip samples in conjunction with detailed geologic mapping on Doyon Land in 2011. Soil samples were collected along ridges and spurs on a nominal spacing of 100 meters resulting in the identification of a northeast trending gold and arsenic anomaly associated with the northeast trending dike swarm. Newmont follow-up soil sampling in 2012 consisted of grid soil sampling a 2 kilometer by 5 kilometer area. Anomalous gold was found to be associated with veins bearing quartz- sericite in altered rhyolite dikes (Newmont Mining Corp., 2012, 2013).
Geologic map unit (, )
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization The North Shepard prospect is inferred to be Late Cretaceous or early Tertiary based on isotopic age of Mystery Mountains intrusive complex (Moll and others, 1981).
Alteration of deposit Quartz and sericite (Newmont Mining Corp., 2012).

Production and reserves

Workings or exploration Newmont Mining Corporation (2012) collected 466 soil samples and 23 rock chip samples in conjunction with detailed geologic mapping on Doyon Land in 2011. Soil samples were collected along ridges and spurs on a nominal spacing of 100 meters resulting in the identification of a northeast trending gold and arsenic anomaly. Newmont follow-up soil sampling in 2012 consisted of grid soil sampling a 2 kilometer by 5 kilometer area. Anomalous gold was found to be associated with veins bearing quartz- sericite in altered rhyolite dikes. Selected rock chip samples of quartz veins hosted in rhyolite dikes yielded assays of up to 12 ppm gold, whereas, non-quartz veined rock chip samples collected within the northeast trend typically yielded assays of 1 to 3 ppm gold.  In 2012, Newmont drilled 3 NQ size core holes totaling 486 meters designed to intersect the sericite altered rhyolite dikes. Drill intercepts of anomalous gold include 4.9 meters of 3.74 g/t gold in hole number SHEP-0002 and 2.8 meters of 8.07 g/t gold in hole number SHEP-0003 (Newmont Mining Corp., 2012 and Newmont Mining Corp., 2013).
Indication of production None

References

References

Reporters V.C. Zinno (Alaska Earth Sciences, Inc.), F.H. Wilson, (USGS)
Last report date 3/15/2016