Golden Zone

Mine, Active

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities As; Pb; Sb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; pyrite; sphalerite; tetrahedrite
Gangue minerals calcite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale HE
Quadrangle map, 1:63,360-scale A-6
Latitude 63.2138
Longitude -149.6493
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Golden Zone Mine is at the headwaters of Bryn Mawr Creek, a tributary of the West Fork Chulitna River. It 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 1:63,360-scale topographic map. Access is via dirt road from Colorado Station on the Alaska Railroad. The mine is about 0.5 mile west-northwest of the center of section 3, T. 20 S., R. 11 W.. The location is accurate.

Geologic setting

Geologic description

The country rocks in the vicinity of the Golden Zone Mine are Devonian to Triassic clastic, carbonate, volcanic, and volcaniclastic rocks that are intruded by a plug of Upper Cretaceous biotite-quartz-diorite porphyry (Perry and others, 2005; Hidefield, 2008; Kerr and Loveday, 2011). The deposit is in a breccia pipe that measures 250 feet by 300 feet at the surface and tapers downward. The contacts of the pipe dip steeply 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 1,500 feet. The pipe is almost entirely contained in the plug of biotite-quartz-diorite porphyry that is about 600 by 1,000 feet in size at the surface. 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. Major faults in the area trend northeast 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 Postmineral northwest-trending faults cut the breccia (unpublished report by Addwest Minerals International, Ltd., 1997).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 arsenopyrite, pyrite, pyrrhotite, chalcopyrite and sphalerite. Several younger, sulfide-dominated events have overprinted the earlier, relatively barren, quartz-dominated brecciation, producing breccia containing over 10 percent sulfides. The younger breccia can be subdivided into early arsenic-rich zones and older copper-rich zones; the former contain better gold grades, in places up to 5 ounces of gold per ton.
The Golden Zone pipe is marked by extensive alteration and mineral zonation. A lead and zinc halo extends up to 2 miles from the pipe; the gold/silver ratios in arsenopyrite and chalcopyrite show a systematic variation; red bed units around the plug show widespread bleaching (C.C. Hawley, oral communication, 1999). Propylitic haloes consisting of epidote, carbonate minerals, and chlorite are present at the margin of the quartz diorite plug, and hornfels-skarn zones are developed in carbonate-rich country rock. Sericite is the dominant alteration mineral in the breccia; argillic overprinting (?), quartz flooding and Fe-carbonates are also reported, but their paragenesis is unclear.
Since its discovery in 1906, the Golden Zone Mine has been explored on the surface, in underground workings, and by extensive drilling. Through 2008, the property was explored by about 20,100 meters of core and reverse-circulation drilling, extensive trenching, and about 1,200 meters of underground workings on three levels. The details of the exploration and the many companies that have been involved are well documented in Perry and others (2005) and Kerr and Loveday (2011). Close-spaced helicopter aeromagnetic and EM geophysical surveys have been flown over the mine; some ground-based IP work has been done as well. The State of Alaska sponsored an aeromagnetic survey in 1996 that included the mine site (Burns, 1997).
In 2011, Alix Resources Corp. (2012) drilled 7 holes. Two holes totaling 574 meters were in the breccia pipe; the best intercept was 256 meters with 1.50 gram of gold per tonne, 12.15 grams of silver per ton and 0.11 percent copper. Three holes were drilled at the GAS prospect south of the breccia pipe; numerous intercepts contained more than 0.1 gram of gold per ton but the highest was only 0.80 gram of gold per tonne. Two holes were drilled across the BLT zone on the northeast side of the breccia pipe. One was abandoned at 22 meters. The other was 178 meters deep; the best intercept was 4.0 meters with 0.77 gram of gold per tonne, 4.5 grams of silver per tonne, and 0.03 percent copper.
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).
Alix Resources Corp. entered into option agreement with Hidefield Gold Inc. and Mines Trust Company on the Golden Zone mine in 2010 and commissioned a new study of the deposit using new and reinterpreted drilling and analyses (Kerr and Loveday, 2011). The work included a new estimate of the resources in 0.5-grams-of-gold-per-tonne steps from 0.5 gram to 4.0 grams. The estimate is lengthy and should be consulted in its entirely for a complete picture. However, to use an estimate near the midpoint of their cutoff grades: 1) at a cutoff of 1.5 grams of gold per tonne, the Golden Zone has a combined measured and indicated resource of about 1.679 million tonnes with an average grade of 4.33 grams of gold per tonne, 20.94 grams of silver per tonne, and 0.11 percent copper; and 2) at a cutoff grade of 1.0 gram of gold per tonne, it has an inferred resource of 186,181 tonnes with an average grade of 1.52 grams of gold per tonne, 6.49 grams of silver per tonne, and 0.4 percent copper.
In 2016, Avidian Gold Inc. purchased Hidefield Gold PLC’s 29.4 percent interest outright, and entered into a purchase agreement with Chulitna & Mines Trust to acquire the remaining 70.6 percent interest in the Golden Zone property (Athey and Werdon, 2017).
Geologic map unit (-149.651591636096, 63.2133260113723)
Mineral deposit model Polymetallic vein and Au-Ag breccia pipe or Cu-Au porphyry (Cox and Singer, 1986; models 22c, 20c).
Mineral deposit model number 22c, 20c
Age of mineralization The Golden Zone is a magma-driven breccia pipe. Both the intrusion and the breccia minerals are Late Cretaceous (65-70 Ma) (Swainbank and others, 1977).
Alteration of deposit The Golden Zone pipe is marked by extensive alteration and mineral zonation. Propylitic haloes consisting of epidote, carbonate minerals, and chlorite are present at the margin of the quartz diorite plug, and hornfels-skarn zones are developed in carbonate-rich country rock. Sericite is the dominant alteration mineral in the breccia; argillic overprinting(?), quartz flooding and Fe-carbonates are also reported, but their paragenesis is unclear.

Production and reserves

Workings or exploration Since its discovery in 1906, the Golden Zone Mine was been explored on the surface, in underground workings, and by extensive drilling. Through 2008, the property has been explored by about 20,100 meters of core and reverse-circulation drilling, extensive trenching, and about 1,200 meters of underground workings on three levels. Closely-spaced helicopter aeromagnetic and EM geophysical surveys have been flown over the mine; some ground-based IP work has been done as well. The State of Alaska sponsored an aeromagnetic survey in 1996 that included the mine site (Burns, 1997). As of early 2011, the Golden Zone Mine has been optioned by the Alix Resources Corp. who drilled 7 holes in 2011.
Indication of production Yes; small
Reserve estimates
Kerr and Loveday (2011) estimated the resources of the Gold Zone Mine in 0.5-grams-of-gold-per-tonne steps from 0.5 gram to 4.0 grams. The estimate is lengthy and should be consulted in its entirely for a complete picture. However, using an estimate near the midpoint of their cutoff grades: 1) at a cutoff of 1.5 grams of gold per ton, the Golden Zone has a combined measured and indicated resource of 1,679,596 tonnes of ore with an average grade of 4.33 grams of gold per tonne, 20.94 grams of silver per tonne, and 0.11 percent copper; and 2) at a cutoff grade of 1.0 gram of gold per tonne, it has an inferred resource of 186,181 tonnes with an average grade of 1.52 grams of gold per tonne, 6.49 grams of silver per tonne, and 0.4 percent copper.
The Golden Zone property hosts a number of high-grade gold occurrences, and in 2016, Avidian released a NI 43-101-compliant indicated gold resource of 4.187 million tonnes of material at a grade of 1.99 grams of gold per tonne, for total contained 267,400 ounces of gold, at a cut-off grade of 0.5 gram of gold per tonne in one of the occurrences that remains open and not fully tested (Avidian, 2016).
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).

References

MRDS Number A011313; D000304

References

Alix Resources Corp., 2011, Gold Zone, Alaska (Gold): http://www.alixresources.com/index.php?page=project&project=6 (as of Feb. 15, 2011).
Alix Resources Corp., 2012, Alix announces completion of 2011 program at the Golden Zone property, Alaska: http://www.alixresources.com/index.php?page=news&id=1104 (News release, Jan 5, 2012).
Hawley, C.C., and Van Wyck, 2002-2003, Mines Trust Company, Golden Zone Project, Summary Report.
Hidefield Gold Plc., 2008, Golden Zone: http://www.hidefieldgold.com/s/GoldenZone.asp (as of May 24, 2008).
Kerr, S.R., and Loveday, Derek, 2011, Technical report, Golden Zone property, Alaska, USA: Technical report for Alix Resources Corporation, 115 p. (posted on www.sedar.com, Jan 18, 2011).
Perry, Ian, Braithwaite, Scott, and Davis, Bruce, 2005, Independent technical report on the Golden Zone property, Alaska, USA: http://www.hidefieldgold.com/in/pdf/goldenzone-43101.pdf, 106 p. (as of May 24, 2008).
Reporters N. Van Wyck (Stevens Exploration Management Corporation); D.J. Grybeck (Contractor, USGS); F.H. Wilson (USGS); M.B. Werdon (DGGS)
Last report date 8/26/2017