Shoeshine

Prospect, Active

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As; Cu; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; pyrite; pyrrhotite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale TY
Quadrangle map, 1:63,360-scale D-8
Latitude 61.8278
Longitude -152.8869
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Shoeshine prospect is on the east-facing slopes of peak 6952, about 2.0 miles southeast of Mount Estelle. It is about 0.4 mile northwest of the center of section 15, T. 20 N., R. 20 W., of the Seward Meridian. The center of the prospect location is accurate to within 500 feet.

Geologic setting

Geologic description

The Shoeshine prospect is in the Cretaceous (65-66 Ma) Mount Estelle pluton, which is zoned from a granite core to marginal phases of quartz monzonite, quartz monzodiorite, augite monzodiorite, diorite, and lamprophyric mafic and ultramafic rocks. The pluton intrudes Jurassic and Cretaceous sedimentary rocks that are hornfelsed adjacent to the pluton, are locally stained red, and have been altered to sericite and clay. Pyrite occurs as disseminations and along fractures (Reed and Elliott, 1970; Millholland, 1995; Crowe and others, 1991; Crowe and Millholland, 1990).
The highest grades of mineralization and the most significant alteration in the Shoeshine area occur in the leucocratic phase of the composite pluton, one of five igneous phases mapped at this prospect. Intrusion-hosted mineralization is represented by multi-episodic quartz vein arrays. In one location, a 300 meter wide sheeted vein swarm has been traced for a strike length of more than 1 kilometer and through a vertical range of up to 200 meters. Individual veins, ranging from several millimeters to 20 centimeters thick, have assayed greater than 200 grams of gold per tonne (Millrock Resources Inc., 2014).
There was considerable work in the area by government and industry as far back as the 1970's that identified mineralization, but the work was more general than prospect specific (see TY019). From 2005 to 2008, several companies (Hidefield Gold Plc. (2008), International Tower Hill Mines Ltd. (2007), and Millrock Resources Inc. (2008)) have defined several specific prospects in the area, including the Shoeshine prospect. In 2011, Millrock explored the Shoeshine prospect as part of their Estelle project, which covers a large block of claims north and south of Mount Estelle (Millrock Resources Inc., 2011).
International Tower Hill (2007) collected 3 samples of quartz-sulfide veins at the Shoeshine prospect that contained 63 to 238 parts per million (ppm) gold, 14 to 389 ppm silver, 0.3 to 1.0 ppm copper, and 0.0 to 2.0 ppm lead. The veins trend north-northwest and dip steeply to the northeast or southwest. Millrock collected numerous samples in an area about 3,500 feet by 2,500 feet in size on the east slope of peak 6952; many of the samples contained more than 2.0 grams of gold per ton. Of the 58 samples they collected, the average gold content was 5.29 grams per tonne; the minimum was 0.09 gram of gold per tonne, and the highest value was 238.0 grams of gold per tonne. The porphyry-style(?) mineralization consists mainly of quartz-arsenopyrite veins; auriferous quartz stockworks; and breccia zones cemented by quartz, oxidized sulfides, and tourmaline.
In 2011, Millrock drilled a 388.8-meter hole that went through altered, mineralized rock for most of its length. The mineralization consists of narrow quartz veins and disseminated sulfides. Gold is associated with arsenopyrite and minor chalcopyrite. The best intercept was 241.8 meters that averaged 0.24 gram of gold per tonne; this included 8.32 meters that averaged 1.18 grams of gold per tonne and 5.82 meters that average 1.62 grams of gold per tonne (Millrock Resources Inc., 2011).
Geologic map unit (-152.889720390627, 61.827203648669)
Mineral deposit model Auriferous, arsenopyrite-quartz veins and stockworks (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Late Cretaceous/early Tertiary?; mineralization in the area is thought to be related to the 65 to 66 Ma granodiorite of Mount Estelle (Millrock Resources Inc., 2014).
Alteration of deposit Plutons have hornfelsed adjacent sedimentary rocks, which may be locally stained red and altered to sericite and clay (Reed and Elliott, 1970; Millholland, 1995; Crowe and others, 1991; Crowe and Millholland, 1990). Quartz + gold in multi-episodic quartz vein arrays are present in intrusion-hosted mineralization. Extensive but otherwise undefined (Millrock Resources Inc., 2014).

Production and reserves

Workings or exploration There was considerable work in the area by government and industry as far back as the 1970's that identified mineralization, but the work was more general than prospect specific (see TY019). From 2005 to 2008, several companies (Hidefield Gold Plc. (2008), International Tower Hill Mines Ltd. (2007), and Millrock Resources Inc. (2008)) have defined several specific prospects in the area, including the Shoeshine. Millrock explored the deposit as part of its Estelle project, which covers a large block of claims north and south of Mount Estelle. They drilled one hole in 2011; the best intercept was 241.8 meters that averaged 0.24 gram of gold per tonne; this included 8.32 meters that averaged 1.18 grams of gold per tonne and 5.82 meters that average 1.62 grams of gold per tonne (Millrock Resources Inc., 2011).
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Crowe, D.E., and Millholland, M.A., 1990, High-grade gold mineralization associated with high salinity hydrothermal fluids, Mt. Estelle pluton, central Alaska Range [abs.]: Geological Society of America, Abstracts with Programs, v. 22, p. A41.
Hidefield Gold Plc., 2008, South Estelle: http://www.hidefieldgold.com/s/SouthEstelle.asp (as of May 25, 2008).
International Tower Hill Mines Ltd., 2007, ITH further defines mineralization at South Estelle: (News release, October 18, 2007) http://www.ithmines.com/archives/past_news_releases/index.php?&content_id=165 (as of January 7, 2015).
Millholland, M.A., 1995, Geology and discovery at Mount Estelle: Newsletter of the Alaska Geological Society, v. 24, no. 8, p. 1.
Millrock Resources Inc., 2008, Estelle: http://www.millrockresources.com/index.php/projects/estelle/ (as of May 25, 2008).
Millrock Resources Inc., 2011, Millrock reports additional drill results from Estelle project, Alaska: (News release, December 8, 2011) http://www.millrockresources.com/news/millrock-reports-additional-drill-results-from-estelle-project-alaska (as of January 7, 2015).
Millrock Resources Inc., 2014, Estelle: http://www.millrockresources.com/projects/estelle/ (as of January 7, 2014).
Reporters D.J. Grybeck (Contractor, USGS); V.C. Zinno (Alaska Earth Sciences, Inc.)
Last report date 1/7/2015