Southwest Grubstake

Occurrence, Active

Commodities and mineralogy

Main commodities Ag; Au; Pb; Zn
Other commodities Ba
Ore minerals barite; galena; gold; magnetite
Gangue minerals biotite; dolomite; quartz

Geographic location

Quadrangle map, 1:250,000-scale GU
Quadrangle map, 1:63,360-scale D-1
Latitude 62.892
Longitude -144.038
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Southwest Grubstake target is about 12.7 miles north-northwest of Slana. It is about 3.4 miles northwest of VABM 6677 'Ahtell' and about 0.2 mile southwest of the center of section 23, T. 13 N., R. 7 E., of the Copper River Meridian. The location is accurate within 1/4 mile.

Geologic setting

Geologic description

This occurrence is part of the Chisna Project; operated as of 2014 by Corvus Gold Inc. Stream sediment surveying and geological mapping in the greater area identified several areas with alteration and mineralization styles that are typical of high level porphyry-type alteration including potassic alteration with biotite and magnetite veining. Mineralization is generally hosted in Permian-Triassic volcanic rocks which have been intruded by Jurassic and Cretaceous mafic and felsic intrusions (Corvus Gold Inc., 2014).
Southwest Grubstake is a mineral occurrence that presents as a series of en-echelon quartz-dolomite-barite veins up to 2 meters wide defined over a 600-meter-long trend. These polymetallic quartz veins have returned high gold values along with significant silver, lead and zinc values from veins ranging in width from 20 cm up to 2 meters. This vein swarm, which strikes NNE to NE within a NW to SW mineralized trend, has been delineated over a strike length in excess of 600 meters. A total of 19 rock samples derived from in-place quartz-dolomite-barite boulder trains and outcrops returned an average of 7.38 grams per tonne gold, 8.82 grams per tonne silver, 0.91 percent lead and 0.16 percent zinc, with highs of 46.5 grams per tonne gold, 29.8 grams per tonne silver, 4.22 percent lead and 1.22 percent zinc (Corvus Gold Inc., 2014).
Mapping of vein lengths and density, and determination of the relationship between this veined mineralization and the adjacent Grubstake copper-gold porphyry system, was the primary focus of 2011 exploration in advance of drilling (Corvus Gold Inc., 2014).
Geologic map unit (, )
Mineral deposit model Porphyry Cu-Au (Cox and Singer, 1986; model 20c)
Mineral deposit model number 20c
Age of mineralization Younger than the Permian - Triassic host rocks (Corvus Gold, 2014).
Alteration of deposit Potassic alteration with biotite and magnetite veining (Corvus Gold, 2014).

Production and reserves

Workings or exploration
Corvus Gold Inc., in a joint venture with Ocean Park, discovered the Southwest Grubstake target from the results of surface exploration in summer 2010 (Corvus Gold Inc., 2011).
In summer 2011, Corvus conducted an exploration program that included mapping of vein lengths and density, and determination of the relationship between this veined mineralization and the adjacent Grubstake copper-gold porphyry system. Corvus reported that rock samples from networks of quartz-galena-barite veins at the Southwest Grubstake prospect have produced a large number of high grades samples with gold values of over 5 parts per million (Corvus Gold Inc., 2011).
Indication of production None
Reserve estimates None.
Production notes None.