Discovery Zone

Prospect, Active

Commodities and mineralogy

Main commodities Ag; As; Au; Cu; Pb; Sb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; gold; pyrite; sphalerite; stibnite
Gangue minerals carbonates; quartz

Geographic location

Quadrangle map, 1:250,000-scale TC
Quadrangle map, 1:63,360-scale B-6
Latitude 63.2846
Longitude -143.8329
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Discovery Zone prospect is about 3.6 miles north of the junction of the Tok River and Stibnite Creek. It is at an elevation of about 4350 feet and about 0.3 mile northwest of the center of section 2, T. 17 N., R. 8 E., of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Discovery Zone prospect is one of several similar deposits in a mineral belt about 4 miles long that is called the Tushtena project by the current (2010) operator, Triton Gold Ltd. (Newkirk and others, 1986; DiMarchi and others, 1987; Fonseca, 2009). Work along the belt began in 1976 when Resource Associates of Alaska began geochemical sampling in the area. They soon staked claims over the Discovery Zone prospect on what was then considered massive-sulfide mineralization. Their work continued through 1987 in conjunction with several partners and consisted of geologic mapping, rock and soil sampling, and geophysical surveys along what became a belt of deposits. They drilled 17 holes along the belt in 1986 and 8 holes in 1987, totaling 3,390 meters. From 1998 to 2001, Inmet Mining Corporation and Pacific Northwest Resources Company did additional mapping and rock and soil surveys. They diamond drilled 8 more holes totaling 1,489 meters. The property was idle until 2007 when James DeMarchi staked 40 claims over the belt and transferred them to Tushtena Resources Ltd. In 2008, they entered into a joint agreement with Triton Gold.
The rocks along the belt consist of two main units: the Devonian to Precambrian, Macomb Belt unit to the east and the Devonian Tushtena Pass unit to the west. They are separated by the Itra Fault, a regional scale, shallowly to moderately dipping thrust fault (Newkirk and others, 1986; DiMarchi and others, 1987; Fonseca, 2009). The Macomb Belt rocks consist mainly of felsic metatuff and volcaniclastic rocks, and sericite-carbonate-quartz phyllonite. The Tushtena Pass unit consists of schist and phyllite, metadiorite, and lithic tuff.
There are two main styles of mineralization along the belt: 1) hanging-wall, bonanza-style vein systems; and 2) footwall, sulfide stockwork and breccia vein systems. The hanging-wall, vein-type mineralization has an arsenic-lead-zinc association with narrow or no alteration envelopes and is characterized by quartz-carbonate-sulfide-gold-mica veins. The footwall, stockwork-breccia zones have a gold-rich core and peripheral antimony-rich mineralization. The deposits are correlative with others along the Tintina gold belt; the key characteristics are the low angle faults that trap the mineralization and the carbonaceous rocks that provide the right chemistry for deposition.
The Discovery Zone was initially classified as a volcanogenic, exhalative and carbonate, massive-sulfide deposit. But magnetite skarns and gold veins were also identified (Newkirk and others, 1986; DiMarchi and others, 1987; Fonseca, 2009; ). High grade mineralization is found only in Tushtena Unit rocks above the Itra fault. Four types of veins are reported: 1) metamorphic, gold-deficient, quartz veins with disseminated base-metal minerals parallel to foliation; 2) post-metamorphic quartz-gold veins with base-metal sulfides; 3) quartz +/- carbonate veins with chalcedony, clay, and hematite; and 4) alunite-clay-iron oxide-quartz veins. The veins and vein breccias vary from 0.3 to 9 meters thick and are usually in short segments truncated by northeast-trending fractures. The veins have weak, thin alteration haloes with an inner zone of silicification and an outer zone of weak to moderate, iron-magnesium carbonate alteration. High gold values are typically related to abundant arsenopyrite. Numerous intervals in the 13 drill holes in the Discovery Zone prospect contained more than 400 parts per billion (ppb) gold, and many intervals had more than 1,000 ppb gold. The most notable were 116 feet with 1,064 ppb gold, 4,283 parts per million (ppm) arsenic, and 2.80 ppm silver; this included an 2.7-foot interval with 37,028 ppb gold, 33,018 ppm arsenic, and 48.40 ppm silver. An 8.0-foot zone contained 5,037 ppb gold, 11,736 ppm arsenic, and 1.55 ppm silver; this included 0.5 feet with 18,200 ppb gold, 27,500 ppm arsenic, and 5,80 ppm silver.
Geologic map unit (-143.835145275214, 63.2842324672489)
Mineral deposit model Tintina-style, gold-arsenopyrite-quartz veins.
Age of mineralization About 70 to 105 Ma by analogy, if Tintina-style mineralization.
Alteration of deposit The veins have weak, thin alteration haloes with an inner zone of silicification and and an outer zone of weak to moderate, iron-magnesium carbonate alteration.

Production and reserves

Workings or exploration The Discovery Zone prospect is one of several similar deposits in a mineral belt about 4 miles long that is called the Tushtena project by the current (2010) operator, Triton Gold Ltd. (Newkirk and others, 1986; DiMarchi and others, 1987; Fonseca, 2009). Work along the belt began in 1976 when Resource Associates of Alaska began geochemical sampling in the area. They soon staked claims over the Discovery Zone prospect on what was then considered massive-sulfide mineralization. Their work continued through 1987 in conjunction with several partners and consisted of geologic mapping, rock and soil sampling, and geophysical surveys along what became a belt of deposits. They drilled 17 holes along the belt in 1986 and 8 holes in 1987, totaling 3,390 meters. From 1998 to 2001, Inmet Mining Corporation and Pacific Northwest Resources Company did additional mapping, and rock and soil surveys; they diamond drilled 8 more holes totaling 1,489 meters. The property was idle until 2007 when James DeMarchi staked 40 claims over the belt and transferred them to Tushtena Resources Ltd. In 2008, they entered into a joint agreement with Triton Gold.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

1986 Annual Report - Volume 1. Resource Associates of Alaska Inc.. Internal Report, 141 p.
DiMarchi, J.J., Oreskes, N., Newkirk, S.R. and Hanneman, N.L., 1987. AR/TRIO 1987 Annual Report.
Fonseca, Anna, 2009, Technical report on the Tushtena gold property, Delta Mineral District, Alaska: Technical Report for Triton Gold Limited, 67 p. (as of February 1, 2010, posted on the Internet at: http://www.tritongold.com.au/docs/Alaskan_Project_Independent_Geologists_Report.pdf).
Newkirk, S. R., Muntzert, J. K., Puchner, C. C., Hanneman, N. L., and Flanders, R. W., 1986, AR JV
Resource Associates of Alaska Inc.. Internal Report, 111 p.
Reporters D.J. Grybeck (Contractor, U.S. Geological Survey)
Last report date 4/2/2010