|Quadrangle map, 1:250,000-scale||TN|
|Quadrangle map, 1:63,360-scale||B-6|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The West Tanana prospect covers much of the western half of section 23, the northeast one-quarter of section 22, and the SE1/4 of section 15, T. 5 N., R. 26 W., of the Fairbanks Meridian. The coordinates are at about the center of this prospect which is about 1 mile north-northwest of the junction of Monday and Grant Creek.|
The West Tanana prospect is on the southwest flank of Grant Dome in a broad divide that separates Monday and Lynx creeks. The bedrock in the area is black graphitic schist, quartz-muscovite schist, chert, and quartzite (WGM, Inc., 1998). The closest intrusive rock known in the area is the Cretaceous Melozitna pluton, which crops out about 8 miles northwest of the prospect (Chapman and others, 1982). Boulders of a diorite dike are in gravel at the American Creek placer mine, about 2 miles to the northwest (TN015) (WGM, Inc., 1998).
Although placer gold was mined in the early 1900s from nearby Grant Creek (TN071), more recent work has focused on exploring the area for lode deposits. DiMarchi (1991) postulated that concentric rings identified in air photos of Lynx Dome may represent a granitic cupola associated with mineralization. Anomalous values of 1-3 parts per million (ppm) molybdenum in geochemical samples support this possibility. Concentric circular features and intersecting lineaments at Ring Hill also suggest a buried pluton there.
During the 1990 season, 121 soil, 12 rock, and 5 stream-sediment samples were collected by Central Alaska Gold Company (DiMarchi, 1991). The sampling program delineated an area up to 5,000 feet wide of anomalous gold and arsenic values, including 15 samples with gold values between 30 and 910 parts per billion (ppb) and arsenic as high as 1,510 ppm.
Trenches dug by Central Alaska Gold Company in 1991 intersected several gold-bearing shear zones that trend N10E and dip 20W. Samples show high arsenic, barium, iron, strontium and phosphorus values. Platinum and palladium values are also elevated, but silver and base metal values are low.
Ventures Resource Corporation (1997) reported that west of Monday Creek there is a broad area of gold geochemical anomalies, quartz veins, and altered zones of silification, iron oxide and clay. Of 64 samples, 16 contained gold ranging from 50 to 580 ppb. These samples average twice background levels of arsenic and contain weakly anomalous phosphorus.
WGM, Inc., explored the Ring Hill-Monday Creek area in 1997. Their work confirmed that several large, northeast-trending, as well as smaller, northwest-trending, faults cut the prospect area (WGM, Inc., 1998). These faults may be conjugate sets associated with the east-west trending, right-lateral Kaltag fault. The northeasterly structures are traceable for up to 12 miles, and cut across Lynx Creek and Grant Creek. Silicification appears to have occurred along all of the faults; silicified country rocks up to 1,000 feet from the faults contain up to 5 percent sulfides, mostly pyrite.In 2006, International Tower Hill Mines, Ltd. (2007, Drilling; 2008, West Tanana) began geochemical soil surveys and mapping in this area under a exploration agreement with Doyon, Ltd. They defined a geochemical anomaly in gold, bismuth, and tellurium, about 1 kilometer in diameter. Samples from old trenches and outcrops contained 5.7 to 17.6 ppm gold, up to 11.8 ppm silver, less than 5 ppm to 1 percent arsenic, less than 2 to 96 ppm bismuth, less than 0.05 to 3.95 ppm tellurium, and minor copper, lead, zinc, and antimony. Drilling in 2007 defined a shallow, east-dipping zone of gold mineralization about 30 meters wide. Notable intercepts include 0.3 meters with 15.6 grams of gold per ton and a 4.3 meter breccia zone with 2.5 grams of gold per ton. The mineralization seems to be associated with a series of north-northeast-trending structures. The prospect is considered to be a stacked Pogo-type vein system.
|Geologic map unit||(-152.870120524913, 65.2468627806509)|
|Mineral deposit model||Pogo-type Au-Bi-Te-quartz veins?|
|Age of mineralization||Mineralization may be Cretaceous based on the age of the nearby Melozitna Pluton.|
|Alteration of deposit||Silicification and pyritization; iron oxide and clay.|
|Workings or exploration||Although placer gold was first mined in the early 1900s from nearby Grant Creek (TN071), more recent work has focused on exploring the area for lode deposits and trenches were dug by Central Alaska Gold Co. in 1991 (DiMarchi, 1991) that intersected several gold-bearing shear zones. In 1996 Dighem Surveys of Toronto Canada flew magnetic and electromagnetic surveys, and Ventures Resource Corporation worked in the area. WGM, Inc. worked in on the prospect in 1997 and carried out a soil geochemical survey over an area of about 2 square miles (WGM, Inc., 1998). In 2006, International Tower Hill Mines, Ltd. (2007, Drilling; 2008, West Tanana) began soil geochemical surveys and surface mapping under a exploration agreement with Doyon, Ltd. Drilling in 2007 defined a shallow, east-dipping zone of gold mineralization about 30 metes wide.|
|Indication of production||None|
Additional commentsThe prospect lies on land leased or owned by Doyon, Ltd.
Chapman, R.M., Yeend, W.E., Brosge, W.P., and Reiser, H.N., 1982, Reconnaissance geologic map of the Tanana quadrangle: U.S. Geological Survey Open-File Report 82-734, 20 p., scale 1:250,000.
DiMarchi, J.J., 1991, Doyon, Ltd., Report 91-8a: Unpublished report held by Doyon, Ltd., Fairbanks, Alaska.
International Tower Hill Mines Ltd., 2007 (Drilling), ITH reports initial drilling results at West Tanana project, central Alaska. (September 18, 2007).
International Tower Hill Mines Ltd., 2008 (West Tanana): http://www.ithmines.com/s/WestTanana.asp (as of March 4, 2008).
McCoy, Dan, Newberry, R.J., Layer, Paul, DiMarchi, J.J., Bakke, Arne, Masterman, J.S., and Minehane, D.L., 1997, Plutonic-related gold deposits of interior Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 191-241.
Ventures Resource Corporation, 1997, Doyon, Ltd., Report 97-27: Unpublished report held by Doyon, Ltd., Fairbanks, Alaska.
WGM Inc., 1998, Doyon, Ltd., Report 98-28: Unpublished report held by Doyon, Ltd., Fairbanks, Alaska.
|Reporters||G.E. Graham (ADGGS); D.J. Grybeck (Port Ludlow, WA)|
|Last report date||3/4/2008|