Pogo

Prospect in Alaska, United States with commodities Gold, Silver, Arsenic, Bismuth, Copper, Molybdenum, Lead, Tellurium, Zinc

Geologic information

Identification information

Deposit ID 10307233
Record type Site
Current site name Pogo
Alternate or previous names Liese Creek

Geographic coordinates

Geographic coordinates: -144.91282, 64.45271 (WGS84)
Relative position The Pogo deposit is located on the Goodpaster River drainage approximately 5 miles north of the mouth of Central Creek (BD011), and approximately 35 miles northeast of Big Delta. The prospect is part of a 72 square-mile claim block that includes Sonora Creek (BD049) and parts of Central Creek. The approximate center of the Pogo deposit is in section 26, T. 25 S., R. 14 E., of the Fairbanks Meridian, which is bordered on the north and south by Liese Creek and Pogo Creek. A winter trail from Big Delta provides access up the Goodpaster River. The base camp of operations, a 24-trailer exploration camp, is located at SE1/4SE1/4 section 27, T. 5 S., R. 14 E., of the Fairbanks Meridian. A 1,500-foot airstrip is also located at the site. The Pogo prospect was not identified as a separate location by Cobb (1972) or by Cobb and Eberlein (1980).
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Silver Secondary
Arsenic Secondary
Bismuth Secondary
Copper Secondary
Molybdenum Secondary
Lead Secondary
Tellurium Secondary
Zinc Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Bismuth Ore
Bismuthinite Ore
Chalcopyrite Ore
Gold Ore
Pyrite Ore
Pyrrhotite Ore
Sphalerite Ore
Tetradymite Ore
Lollingite Ore
Maldonite Ore
Biotite Gangue
Dolomite Gangue
Feldspar Gangue
Quartz Gangue
Sericite Gangue

Alteration

  • (Local) The Liese Zones all are associated with vein and replacement type textures. The veining textures are characterized by two styles of quartz veins and alteration assemblages. The early veins are typified by white quartz containing arsenopyrite, chalcopyrite, pyrite, pyrrhotite and loellingite with secondary biotite in selvages up to 1 meter in width. The later veins are typified by gray quartz as stockwork veins and replacement selvages containing arsenopyrite and pyrite, along with secondary disseminated sericite and dolomite. It is common to find the sericite-dolomite alteration overprinted upon the earlier secondary biotite. Some silica flooding is observed in the gneiss and intrusive (M. Smith, oral communication, 1999).

Nearby scientific data

(1) -144.91282, 64.45271

Comments on the geologic information

  • Geologic Description = The regional bedrock is composed of high grade gneisses intruded by Cretaceous granitic bodies. The area is predominantly cut by northwest-trending high-angle faults. However, there are other high-angle faults with various orientations. To the north, the region is intruded by the Cretaceous Goodpaster Batholith. At the Pogo deposit the host rock is predominantly biotite-quartz-feldspar amphibolite-grade gneiss. In the Liese Creek drainage, a series of granodiorite dikes intrude the gneisses. These dikes are interpreted to be related to the batholith. The youngest geologic unit in the area is a northwest-trending, steeply dipping, diorite dike situated in Liese Creek. This dike partly cuts off mineralization on the northeast edge of the deposit (Teck Resources Inc., 1998). . The Pogo deposit underlies a 1-square-mile area with soil geochemistry analyses greater than 100 ppb Au. Subsurface drilling has revealed several distinct zones of gold mineralization. These zones are roughly flat lying, vertically stacked, tabular in shape, and subparallel to each other. The Pogo deposit is divided along a flexure point with an almost sinusoidal wave shape. The west portion of the deposit strikes northeast and dips northwest about 30 degrees. The east portion of the deposit strikes east and dips north about 30 degrees. The upper Liese Zone (L1) is the largest and shallowest of the zones. It is at least 4000 by 2000 feet and varies from 0 to 65 feet in thickness. The lower Liese zone (L2) lies 300 to 500 feet below the L1. It is generally thinner, but higher grade than the L1. The L3 zone is a mineralized section approximately 800 feet below L1, intercepted by two drill holes (Smith, 1999). Its size and shape have not yet been defined. Although there are no mappable thrust faults, the zones of mineralization cut the foliation of the host rock by 15 degrees. These zones are interpreted to occur along low angle structures. In addition, the area is predominantly cut by northwest-trending high-angle faults. However, a north trending, high angle fault zone in the north-central part of the deposit has been tentatively identified as the feeder zone for the deposit. This zone is composed of 225 feet of intermittent quartz in sheared gneiss containing 0.25 ounces/ton Au (M. Smith, oral communication, 1999). All of the mineralized zones are predominantly quartz carrying approximately 3% sulfides. Minerals found within the quartz include arsenopyrite, bismuth, bismuthinite, chalcopyrite, gold, loellingite, maldonite, pyrite, pyrrhotite, sphalerite, and tetradymite (Smith, 1999). The gold occurs as 1 to 25 micron grains in arsenopyrite along fractures, and as inclusions in bismuth, tetradymite, and other various Au-Pb-Bi-Te +/- S minerals. Geochemical data suggest a strong correlation between gold and bismuth, and a weaker correlation between gold and other lithophile elements (Smith, 1999). The Liese Zones all are associated
  • Geologic Description = with vein and replacement type textures. The veining textures are characterized by two styles of quartz veins and alteration assemblages. The early veins are typified by white quartz containing arsenopyrite, chalcopyrite, pyrite, pyrrhotite and loellingite with secondary biotite in selvages up to 1 meter in width (Smith, 1998). The later veins are typified by gray quartz as stockwork veins and replacement selvages containing arsenopyrite and pyrite, along with secondary disseminated sericite and dolomite. It is common to find the sericite-dolomite alteration overprinted upon the earlier secondary biotite. Some silica flooding is observed in the gneiss and intrusive (M. Smith, oral communication, 1999). Geochronology studies have focused on the granodiorite and diorite dikes in the Liese Creek drainage. The diorite dike has an 40Ar/39Ar biotite age of 94 Ma, and a U-Pb zircon age of 94 Ma. The granodiorite dike has an 40Ar/39Ar biotite age of 91.7 Ma, an 40Ar/39Ar white mica age of 91.2 Ma, and a U-Pb monazite age of 107 Ma (M. Smith, oral communication, 1999). . Metallurgical testing has shown that 92 to 94% of the gold is recoverable using conventional flotation and cyanidation of the sulfide concentrate. Currently, reserve estimates are 9.98 million tons with an average grade of 0.52 ounces/ton for 5.21 million total ounces of gold using a cutoff grade of 0.1 ounces/ton gold (Teck Resources Inc., 1998). The Goodpaster region was first explored for placer gold in 1915. Thomas (1970) reports a stampede of prospectors that ended soon after, due to the lack of substantial deposits. A regional stream sediment sampling program identified gold, arsenic, and tungsten anomalies in Liese Creek and Pogo Creek in 1981. From 1991 to 1994, exploration efforts consisted of a soil sampling grid, minor prospecting, and geophysics. Three core drill holes were completed on Liese Creek in 1994. Based on those findings,13 additional core holes were drilled in the area in 1995. This led to the initial identification of the L1 zone. Work in 1996 consisted of 22 drill holes to further define the zone. From 1991 to 1996, the exploration program drilled a total of 36,703 feet of core, and collected 4,142 core samples, and 3,520 geochemical samples. An additional 41 drill holes in 1997 enlarged the deposit and found the lower L2 zone. Drilling in 1998 focused on better defining the inner section of L1 and L2. A total of 91,263 feet of drilling has been completed and 3,404 core samples and 1,500 geochemistry samples have been collected (M. Smith, oral communication, 1999). Other work included exploration, and evaluation of a proposed adit, tailings storage, and plant site. The spatial extent of the subsurface zones are not fully delineated; they are still open to the southeast and northwest. Currently, regional work has identified an 8 mile long trend of anomalous soil geochemistry extending from the Pogo deposit to the southeast (M. Smith, 1998). In addition to infill and step-out drilling, a smaller surface exploration program is planned for 1999. An adit to obtain geotechnical data, test for continuity of the veins, and obtain a bulk sample for metallurgical testing is planned for 1999. The proposed adit will involve the mining and removal of 63,000 cubic yards of rock. Permitting for the adit and associated facilities is in progress (Teck Resources Inc., 1998).
  • Age = Mineralization at the Pogo deposit is thought to be plutonic-related. Geochronology studies have focused on the granodiorite and diorite dikes in the Liese Creek drainage. The diorite dike has an 40Ar/39Ar biotite age of 94 Ma, and a U-Pb zircon age of 94 Ma. The granodiorite dike has an 40Ar/39Ar biotite age of 91.7 Ma, an 40Ar/39Ar white mica age of 91.2 Ma, and a U-Pb monazite age of 107 Ma. (M. Smith, oral communication, 1999).

Economic information

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Active

Mining district

District name Goodpaster

Comments on the production information

  • Production Notes = No production has occurred at the Pogo deposit.

Comments on the reserve resource information

  • Reserves = Metallurgical testing has shown that 92 to 94% of the gold is recoverable using conventional flotation and cyanidation of the sulfide concentrate. Currently, reserve estimates are 9.98 million tons with an average grade of 0.52 opt for 5.21 million total ounces of gold using a cutoff grade of 0.1 opt gold (Teck Resources Inc., 1998).

Comments on the workings information

  • Workings / Exploration = The Goodpaster region was first explored for placer gold in 1915. Thomas (1970) reports a stampede of prospectors that ended soon after, due to the lack of substantial deposits. A regional stream-sediment sampling program identified gold, arsenic, and tungsten anomalies in Liese Creek and Pogo Creek in 1981. From 1991 to 1994, exploration efforts consisted of a soil-sampling grid, minor prospecting, and geophysics. Three core-drill holes were completed on Liese Creek in 1994. Based on those findings,13 additional core holes were drilled in the area in 1995. This led to the initial identification of the L1 zone. Work in 1996 consisted of 22 drill holes to further define the zone. From 1991 to 1996, the exploration program drilled a total of 171,859 feet of core, and collected 9,641 core samples, and 5,508 geochemical samples. An additional 41 drill holes in 1997 enlarged the deposit and found the lower L2 zone. Drilling in 1998 focused on better defining the inner section of L1 and L2. A total of 91,263 feet of drilling has been completed and 3,404 core samples and 1,500 geochemistry samples have been collected (M. Smith, oral communication, 1999). Other work included exploration, and evaluation of a proposed adit, tailings storage, and plant site. The spatial extent of the subsurface zones is not fully delineated; they are still open to the southeast and northwest. Currently, regional work has identified an 8 mile long trend of anomalous soil geochemistry extending from the Pogo deposit to the southeast (M. Smith, 1998). In addition to infill and step-out drilling, a smaller surface exploration program is planned for 1999. An adit to obtain geotechnical data, test for continuity of the veins, and obtain a bulk sample for metallurgical testing is planned for 1999. The proposed adit will involve the mining and removal of 63,000 cubic yards of rock. Permitting for the adit and associated facilities is in progress (Teck Resources Inc., 1998).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF BD033

Bibliographic references

  • Deposit

    Smith, Moira, 1998, 1998 Exploration update on the Pogo property, Goodpaster River district, Alaska [abs.], in Mining, Alaska's State and Native Lands: Anchorage, Alaska: Alaska Miners Association, 1998 Proceedings, p. 65.

  • Deposit

    Teck Resources Inc., 1998, Pogo project advanced exploration program, Stage II application and plan of operations: Teck Resources Inc. report, 75 p.

  • Deposit

    Smith, Moira, 1999, Gold mineralization on the Pogo claims, east-central Alaska [abs.], in Cordilleran Exploration Roundup Proceedings: Vancouver, British Columbia, 16th Cordilleran Exploration Roundup, p. 73.

Comments on the references

  • Primary Reference = M. Smith, 1999

General comments

Subject category Comment text
Deposit Model Name = Shear-hosted, plutonic-related mesothermal
Deposit Other Comments = the Pogo project is a joint venture of Teck Corporation, Sumitomo Metal Mining, and Sumitomo Corporation. The Teck Corporation is the principal operator of the project and can earn a 40% interest in the property.

Reporter information

Type Date Name Affiliation Comment
Reporter 26-APR-99 Cameron S. Rombach Alaska Division of Geological and Geophysical Surveys