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Golden Zone

Producer in Alaska, United States with commodities Silver, Gold, Copper, Lead, Zinc
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Alteration
  8. Mineral occurrence model information
  9. Nearby scientific data
  10. Economic information about the deposit and operations
  11. Mining district
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10308860
MRDS ID A011313
Record type Site
Current site name Golden Zone
Related records 10100957

Geographic coordinates

Geographic coordinates: -149.64983, 63.21358 (WGS84)
Relative position The Golden Zone mine is located at the headwaters of Bryn Mawr Creek, a tributary of the West Fork Chulitna River. The map site is at an elevation of about 3,500 feet, on the north bank of the creek, and about 2,000 feet southwest of the Golden Zone mine symbol on the topographic map. Access is via dirt road from Colorado Station along the north side of the West Fork Chulitna River to the junction with Bryn Mawr Creek. The road crosses the West Fork Chulitna River and climbs southwesterly to the mine site at an approximate elevation of 3,500 feet. The site is in the NW1/4 of sec. 3, T. 20 S., R. 11 W., of the Fairbanks Meridian. The location is accurate to within 1,000 feet.

Site location context

Political divisions (FIPS codes)

Matanuska-Susitna(Borough)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Healy A-6(quadrangle 1:63,360 scale)

Healy S(quadrangle 1:100,000 scale)

Healy(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Chulitna River(hydrologic unit)

Susitna River(hydrologic accounting unit)

South Central Alaska(hydrologic subregion)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary
Copper Secondary
Lead Secondary
Zinc Critical Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Galena Ore
Pyrite Ore
Sphalerite Ore
Tetrahedrite Ore
Calcite Gangue
Quartz Gangue
Sericite Gangue

Alteration

  • Alteration and mineral zonation is present around the Golden Zone pipe. A distal lead and zinc halo is reported up to 2 miles from the pipe; the gold/silver ratios in arsenopyrite and chalcopyrite show a systematic variation; and red-bed sediments show widespread bleaching (C.C. Hawley, oral communication, 1999). Propylitic haloes consisting of epidote-carbonate-chlorite are present at the margin of the quartz diorite stock, and hornfels-skarn zones are in carbonate-rich country rock. Sericite is the dominant alteration mineral in the breccias, and argillic overprinting (?), quartz flooding and Fe-carbonates are also reported, but their paragenesis is as yet unclear.

Mineral occurrence model information

Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Nearby scientific data

(1) -149.64983, 63.21358
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The country rocks in the area of the Golden Zone mine include Devonian to Triassic clastic, carbonate, volcanic, and volcaniclastic strata, which are intruded by an Upper Cretaceous (70-65 Ma) biotite-quartz diorite porphyry plug (Swainbank and others, 1977). The Golden Zone is the most significant deposit in the southwest portion of the Healy quadrangle. The deposit consists mostly of a single breccia pipe that measures 250 by 300 feet at the surface and thins downward. The contacts are steeply dipping except on the northern side where the dips appear to flatten to the north. Drilling has confirmed that the pipe reaches a depth of 650 feet and possibly as deep as 1,500 feet. The pipe is almost entirely contained within a biotite-quartz diorite porphyry plug measuring 600 by 1,000 feet. The breccia pipe was produced by magmatic devolatilization either from the diorite porphyry or from a related intrusion at depth. Both the breccia and the porphyry have been dated at 65-70 Ma (Swainbank and others, 1977). Major faults in the area trend northeast-southwest and have imparted a strong northeast trending fabric to the host rocks. Differential motion along these faults has localized the subsequent emplacement of the biotite-quartz diorite porphyry and mineralizing fluids. Postmineral northwest-trending faults cut the breccia (unpublished report by Addwest Minerals International, Ltd, 1997). Early brecciation produced angular clasts cemented by vuggy, pale-gray quartz and minor amounts of arsenopyrite, pyrite, pyrrhotite, chalcopyrite and sphalerite. Several younger, sulfide-dominated events have overprinted the earlier, relatively barren, quartz-dominated brecciation, producing breccias containing over 10% sulfides. These younger breccias can be subdivided into arsenic-rich zones (earliest) and copper-rich zones (late); the former contains better gold grades - in places up to 5 ounces of gold per ton.
  • Age = The Golden Zone is a magma-driven breccia pipe. Both the intrusion and the breccia minerals are Late Cretaceous (70-65 Ma) in age (Swainbank and others, 1977).

Economic information about the deposit and operations

Development status Producer
Commodity type Metallic

Comments on exploration

  • Status = Active

Mining district

District name Valdez Creek

Comments on the production information

  • Production Notes = The mine produced 49,169 grams of gold, 267,990 grams of silver, and 19 tonnes of copper between 1941 and 1942 (Hawley and Clark, 1974).

Comments on the reserve resource information

  • Reserves = The proven and probable reserves of the breccia pipe and surrounding prospect are 8 million tons containing 0.1 ounce of gold per ton (at a cutoff of 0.02 ounce of gold per ton), or about 800,000 ounces of gold.

Comments on the workings information

  • Workings / Exploration = There are both surface and underground workings at the Golden Zone mine. Exploration between 1936 and 1996 included 54,326 feet of drilling in 137 drill holes (102 core and 35 reverse circulation holes). Numerous trenches and geochemistry samples have been collected. 1,900 feet of underground development has accumulated on the 100, 200 and 500 foot levels. Close-spaced helicopter aeromagnetic and EM geophysical surveys have been flown over the mine, along with some ground-based IP work (unpublished report by Addwest Minerals International Ltd., 1997). The State of Alaska sponsored an aeromagnetic survey in 1996 that included the mine site in 1996 (Burns, 1997). Sulfide-dominated events have overprinted the earlier, relatively barren, quartz-dominated brecciation, producing breccias containing over 10% sulfides. These younger breccias can be subdivided into arsenic-rich zones (earliest) and copper-rich zones (late); the former contains better gold grades - in places up to 5 ounces of gold per ton.

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = Hawley and others, 1978

General comments

Subject category Comment text
Deposit Model Name = Polymetallic vein and Au-Ag breccia pipe or Cu-Au porphyry (Cox and Singer, 1986; models 22c, 20c)
Deposit Model Number = 22c, 20c

Reporter information

Type Date Name Affiliation Comment
Reporter 07-APR-2000 N. Van Wyck Stevens Exploration Management Corporation

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

External references

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.