Tolovana (Freegold)

Mine, Active

Commodities and mineralogy

Main commodities Ag; Au; Sb
Other commodities Cu; Pb
Ore minerals arsenopyrite; boulangerite; galena; gold; jamesonite; sphalerite; stibnite; tetrahedrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale LG
Quadrangle map, 1:63,360-scale A-1
Latitude 65.0634
Longitude -147.4504
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Tolovana prospect is an area of extensive exploration by Freegold Ventures Ltd. that began in 1996 within the Golden Summit Project. The area includes several old prospects and the Tolovana Mine (LG105-106, LG109-110, and LG112) that were previously described individually in ARDF. The location is accurate to within 100 feet.

Geologic setting

Geologic description

The ARDF record for the Tolovana Mine (LG100) gives the details of the mining and geology of the best known and most productive of the deposits in this site. To summarize (from Freeman, 2008), the Tolovana Mine produced about 5,000 ounces of gold prior to 1942. The mineralization consists of quartz veins and stockworks with varying amounts of arsenopyrite, pyrite, boulangerite, jamesonite, tetrahedrite, and stibnite. The country rocks are Paleozoic volcanic rocks, quartzite, and garnet-biotite schist on the north flank of the Cleary antiform. The middle Cretaceous Dolphin granodiorite pluton outcrops over an area about 2,000 feet long and 1,000 feet wide on the south side of the prospect. Regionally, the deposit is part of a east-northeast-trending mineral belt at least six miles long that is related to a series of parallel, northeast-trending fault zones, spaced about 8,000 feet apart. It is also probably continuous with the mineralization at the adjacent Cleary Hill (Freegold) deposit (LG205) to the north. The mineralization is middle Cretaceous (McCoy and others, 1997).
Although the Dolphin intrusive was drilled from 1994 to 1996 and in 1998, there was little exploration of the quartz veins on the prospect from 1941 to 2004. In 2004, Freegold Ventures Ltd., dug 1,790 feet of trenches and drilled 7 core holes that totaled 3,584 feet. The 2004 drilling indicated that the mineralization is a stockwork deposit. In the eastern part of the prospect it is in metamorphic rocks; in the central and western parts it is in the Dolphin intrusive. In 2007, Freegold contracted an extensive drilling program using rotary-air-blast equipment; 170 holes were drilled, totaling 11,449 feet. Numerous samples had significant gold values. The detailed results of this drilling are available in Freeman (2008).
On the basis of their work, Freegold has defined at least two subparallel mineralized structures, the Tolovana Mine structure and the Scheuyemere vein structure, that extend east-northeast more than 1,900 feet from the old Tolovana Mine (LG110). The mineralization is open at both ends and at depth. The mining before World War II was mainly on a few structurally continuous, high-grade quartz veins in a master shear zone. Recent work indicates that the mineralization is much more extensive and structurally complex, complicated by multiple generations of folding, faulting, and mineralization. The extent of the stockwork-type mineralization in the Dolphin intrusive is unknown.
Geologic map unit (-147.452847653384, 65.0629766251034)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Unknown, but perhaps 88.3-90.1 Ma inferred from Ar40/Ar39 radiometric age dates of two sericite samples representing two distinctly different styles of gold mineralization (Abrams and Giroux, 2013).
Alteration of deposit
Chloritization, kaolinitization, silicification and sericitization. Carbonate
alteration, as calcite or less commonly dolomite or iron carbonate, is found locally (Abrams and Giroux, 2013).

Production and reserves

Workings or exploration
Although the Dolphin intrusive was drilled from 1994 to 1996 and in 1998, there was little exploration of the quartz veins on the prospect from 1941 to 2004. In 2004, Freegold Ventures Ltd., dug 1,790 feet of trenches and drilled 7 core holes that totaled 3,584 feet. In 2007, Freegold contracted an extensive drilling program using rotary-air-blast equipment; 170 holes were drilled, totaling 11,449 feet. Numerous samples had significant gold values.
In 2010 a ground based geophysical survey was conducted (Abrams and Giroux, 2013).
In 2011, Freegold completed its first NI-43 101 compliant resource calculation using previous drilling completed in the Dolphin/Tolovana area. Ground-based induced polarization (IP) geophysics and shovel soil sampling was also performed in 2011 (Abrams and Giroux, 2013).
In 2012, the NI-43 101 compliant resource was updated; the zone used in the calculation was deepened and extended to the northeast to include the Clearly Hill area (Abrams and Giroux, 2013).
In 2013, Freegold drilled 10 holes of 11,392 feet and updated the NI-43 101 compliant resource again (Abrams and Giroux, 2013).
Indication of production Yes; small
Reserve estimates The 2013 resource estimate at the Dolphin/Cleary Zone is as follows: Indicated resource (total): With a gold cut-off of 0.30 gram per tonne, 79,800,000 tonnes of 0.66 gram of gold per tonne; contained 1,683,000 ounces gold. Inferred resource (total): With a gold cut-off of 0.30 gram per tonne, 248,060,000 tonnes of 0.61 gram of gold per tonne; contained 4,841,000 ounces gold. (Abrams and Giroux, 2013).
Production notes None.

Additional comments

The Tolovana prospect is an area of extensive exploration by Freegold Ventures Ltd. that began in 1996 within the Golden Summit Project. The area includes several old prospects and the Tolovana Mine (LG105-106, LG109-110, and LG112) that were previously described individually in ARDF. These individual records are retained in ARDF for their geologic detail and history. The work by Freegold, however, has revealed much new mineralization in the area and the company now interprets the deposits in the area as a single system of veins, that they call the 'Cleary Hill vein swarm'.

References

References

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) http://www.sedar.com/GetFile.do?lang=EN&docClass=24&issuerNo=00004004&fileName=/csfsprod/data88/filings/01242796/00000001/k%3A%5CSedar%5Cfilings%5Clivework%5Cwkout%5C19016%5CCS_tech.pdf (as of December 23, 2014).
McCoy, Dan, Newberry, R.J., Layer, Paul, and others, 1997, Pluton-related gold deposits of Interior Alaska, in Goldfarb, R.J., and Miller, L.D., (editors): Economic Geology Monograph 9, p. 191-241.
Reporters D.J. Grybeck (Port Ludlow, WA); V.C. Zinno (Alaska Earth Sciences, Inc.)
Last report date 12/23/2014