Circle Trail Prospect, Fairbanks Mining District, Fairbanks North Star Borough, Alaska, USAi

Regional Level Types
Circle Trail Prospect	Prospect
Fairbanks Mining District	Mining District
Fairbanks North Star Borough	Borough
Alaska	State
USA	Country

Location: The Circle Trail prospect is located on the divide between Too Much Gold Creek, Fairbanks Creek and Wolf Creek; SE1/4 sec. 21, T. 3 N., R. 2 E., of the Fairbanks Meridian.
Geology: Prior to 1969, the divide between Too Much Gold Creek, Fairbanks Creek and Wolf Creeks was host to several producing mines and numerous prospects. The target of all of these mines and prospects was high grade gold mineralization associated with large northwest and northeast trending shear zones. Low grade mineralization was known to be present on these properties within and along the margins of higher grade portions of the shear zones. However, these lower grade zones could not be profitably worked using the existing technology (W. McCarty, oral commun., 1988). In 1969, International Minerals and Chemicals (IMC) conducted an exploration program designed to address the possibility of surface mining the lower grade material in this area. This work had been prompted by the findings presented in Forbes and others (1968) and Pilkington and others (1969) which indicated significant low grade gold and silver mineralization around higher grade quartz-rich portions of the shear zones. IMC conducted trenching and rotary drilling targeted at low grade gold-silver mineralization in surface mineable zones adjacent to previously mined high grade shear zones. These activities resulted in discovery of the Circle Trail prospect. IMC's exploration efforts on the Circle Trail prospect consisted of geological mapping, grid rock and soil sampling, and excavation of 4 dozer trenches totalling 1874 feet (Pilkington, 1970). In order to test the down-dip extent of mineralization picked up in trenches, IMC conducted rotary drilling using a 5-inch-diameter conventional rotary drilling rig (Pilkington, 1970). A total of 12 vertical holes totalling 2,250 feet was drilled on the Circle Trail prospect in 1969. Based on this drilling and trenching IMC calculated reserves of 1,050,000 tons with 0.050 ounces of gold per ton and 2.09 ounces of silver per ton (Pilkington, 1970). In 1988, BP Minerals conducted additional drilling as operator of a joint venture with Fairbanks Exploration Inc. This program was designed to test for the suspected northwest trending shear zones previously mapped in the area. BP Minerals constructed 2,100 feet of new access road and drilled 2,362 feet of reverse circulation drilling in five holes (Klessig, 1988). Based on the work conducted by IMC and BP Minerals, Fairbanks Exploration Inc. estimated indicated reserves for the Circle Trail zone of 449,808 tons grading 0.070 ounces of gold per ton equivalent to a depth of 50 feet (P. Metz, written commun., 1988). No additional work has been conducted on the project since 1988. The following is a summary of some of the characteristics of the Circle Trail prospect (Freeman, 1991). Mineralization is hosted by both northeast-trending gold-silver-sulfosalt-bearing, D2 shear zones and later northwest-trending gold-silver-arsenic-bearing, D3 shear zones. These shears are hosted by flat-lying felsic metavolcanics and metaquartzites of the middle to upper Cleary sequence. Rocks encountered in trenching and drilling include chloritic quartzite, chlorite schist, quartzite and quartz-chlorite-biotite schist. Sulfide minerals have been oxidized to depths that vary from 80 to 340 feet below surface. Below the oxide zone, arsenopyrite, pyrite, boulangerite and jamesonite have been identified. Gold and silver values are not always elevated where iron, arsenic or lead sulfides occur, but sulfides containing these metals usually are present where gold and silver values are anomalous. Drilling intercepted five separate shear zones over a strike length of 1,500 feet and a combined width (perpendicular to strike) of 1,000 feet. The Circle Trail prospect extends along strike for 10,000 feet, is 1,800 feet wide and has been tested over a vertical distance of 700 feet in drilling, trenching and mining. Mineralization remains open in all directions.
Workings: In 1969 International Minerals and Chemicals (IMC) conducted trenching and rotary drilling targeted at low grade gold-silver mineralization in surface mineable zones adjacent to previously mined high grade shear zones. IMC's exploration efforts on the Circle Trail prospect consisted of geological mapping, grid rock and soil sampling and excavation of 4 dozer trenches totalling 1874 feet (Pilkington, 1970). IMC conducted rotary drilling using a 5-inch-diameter rotary drilling rig (Pilkington, 1970). A total of 12 vertical holes totalling 2,250 feet was drilled on the Circle Trail prospect in 1969. In 1988, BP Minerals conducted additional drilling as operator of a joint venture with Fairbanks Exploration Inc. BP Minerals constructed 2,100 feet of new access road and drilled 2,362 feet in five holes by reverse circulation drilling (Klessig, 1988).
Alteration: Sulfide minerals have been oxidized to depths that vary from 80 to 340 feet below surface (Freeman, 1991).

Commodities (Major) - Au; (Minor) - Ag, As, Pb
Development Status: None
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).

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Link to USGS - Alaska:	LG162

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References