Saddle

Prospect, Active

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Sb
Ore minerals gold; silver; stibnite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale LG
Quadrangle map, 1:63,360-scale A-1
Latitude 65.0645
Longitude -147.3646
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Saddle prospect is located on the divide between Wolf Creek and Fairbanks Creek. It is in the NW1/4 sec. 28, T. 3 N., R. 2 E., of the Fairbanks Meridian.

Geologic setting

Geologic description

Note: As of 2008, this site and several others in the vicinity are being explored as a single entity by Freegold Ventures Inc. (Freeman, 2008) Considerable new mineralization has been discovered that indicates this is part of a larger mineralized system that is described as a separate ARDF site (LG206).
Prior to 1969, the divide between Fairbanks and Wolf Creeks was host to several producing mines and numerous prospects. The mineralization sought in all of these mines and prospects was high grade gold mineralization that occurred in several veins along several large northwest- and northeast-trending shear zones. Low grade mineralization was known to be present at the McCarty (LG152), Pioneer (LG155) and Pennsylvania (LG156) mines nearby, 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 of the 1980s (W. McCarty, oral communication, 1988). In 1969, International Minerals and Chemicals (IMC) began an exploration program designed to test the possibility of surface mining the lower grade material in this area. IMC conducted trenching and rotary drilling targeted at low-grade zones adjacent to previously mined high grade shear zones. hese activities resulted in discovery of the Saddle prospect (Pilkington, 1970).
IMC's initial exploration efforts on the Saddle prospect consisted of geological mapping and sampling of four, previously excavated trenches and open cuts. IMC also excavated 5 new trenches totaling 4,299 feet. Initial sampling was conducted in three trenches previously excavated by Keystone Mines Inc. One of these trenches was located in the footwall of the Pennsylvania shear zone, approximately 1,300 feet northeast of the Pioneer shaft (LG155). This trench exposed a schist-hosted quartz-bearing shear zone oriented N 35 E, 65NW. One-foot channel samples collected in the hanging wall of this shear included 9 feet that with 0.9 part per million (ppm) gold and 58.3 ppm silver. The rocks in the trench consisted of iron-, arsenic- and antimony-oxide-stained silver-gray schist.
IMC also sampled two trenches previously excavated by Keystone Mines approximately 500 feet west of the Pioneer shaft. These trenches cut the Pioneer shear zone which trends N 70 W and dips 50 S. The first trench had 17 feet that assayed 0.54 ppm gold and 75.6 ppm silver; the rocks in the trench consisted of brecciated and silicified quartz-mica schist with minor iron- and antimony-oxide staining. The second trench had 25 feet that assayed 5.68 ppm gold and 142.6 ppm silver in silicified and brecciated quartz-mica schist with weak iron-oxide staining.
To test the down-dip extent of the northeast-trending mineralization identified in the trenches, IMC drilled using a 5-inch rotary drilling rig (Pilkington, 1970). Two vertical holes totaling 485 feet were drilled.
Based on the results from their trenching and drilling, IMC inferred reserves of 2,111,000 tons with a grade of 0.037 ounces of gold per ton and 0.46 ounces of silver per ton (Pilkington, 1970). These reserves were considered subeconomic at then-current price of gold and silver and IMC terminated its lease with Keystone Mines Inc. in 1970.
In 1987, Keystone Mines leased their holdings to Fairbanks Exploration Inc. In 1988, BP Minerals, acting as operator of a joint venture with Fairbanks Exploration Inc. drilled 7 holes totaling 3,465 feet to confirm the earlier IMC work (Klessig, 1988).
Geologic map unit (-147.367047867161, 65.0640778392376)
Mineral deposit model Gold-quartz veins.
Age of mineralization Probably about 90 Ma based on analogy with similar gold deposits nearby.
Alteration of deposit Not specifically noted.

Production and reserves

Workings or exploration
In 1969 International Minerals and Chemicals (IMC) began an exploration program designed to address the possibility of surface mining the lower grade material in this area. IMC carried out trenching and rotary drilling targeted at several low-grade zones adjacent to previously mined high-grade shear zones. This resulted in discovery of the Saddle prospect (Pilkington, 1970).
IMC's initial exploration efforts on the Saddle prospect consisted of geological mapping and sampling of four previously excavated trenches and open cuts. IMC also excavated five new dozer trenches totaling 4,299 feet. Initial sampling was conducted in three trenches previously excavated by Keystone Mines Inc. IMC also sampled two dozer trenches previously excavated by Keystone Mines approximately 500 feet west of the Pioneer shaft. IMC used a 5-inch rotary drilling rig to drill two vertical holes that totaled 485 feet (Pilkington, 1970).
In 1987, Keystone Mines leased their holdings to Fairbanks Exploration Inc. In 1988, BP Minerals, acting as operator of a joint venture with Fairbanks Exploration Inc. drilled 7 holes totaling 3,465 feet to confirm the earlier IMC work (Klessig,1988).
Indication of production None
Reserve estimates Based on the results from their trenching and drilling, IMC inferred reserves of 2,111,000 tons with a grade of 0.037 ounces of gold per ton and 0.46 ounces of silver per ton (Pilkington, 1970). These reserves were considered subeconomic at then-current price of gold and silver and IMC terminated its lease with Keystone Mines Inc. in 1970.

References

MRDS Number 10307740

References

Freeman, C.J., 1992, 1991 Golden Summit project final report, volume 2: Historical summary of lode mines and prospects in the Golden Summit project area, Alaska: Avalon Development Corp., 159 p. (Report held by Freegold Recovery Inc. USA, Vancouver, British Columbia.)
Freeman, C.J., 2008, Executive summary report for the Golden Summit project, Fairbanks Mining District, Alaska: Unpublished Technical Report for Freegold Ventures Ltd., 112 p. (posted on www.sedar.com, March 31, 2008).
Klessig, P., 1988, 1987-1988 Summary report for the Cleary Summit JV: BP Minerals America, 9 p.
Reporters C.J. Freeman, J.R. Guidetti Schaefer (Avalon Development Corporation); D.J. Grybeck (Port Ludlow, WA)
Last report date 6/5/2008