Location: In 2005, drilling began on the Terra prospect about 1.5 miles south of the terminus of the glacier at the head of Fish Creek, a headwater tributary to the Post River. The coordinates are at that location. However, the property consists of a large block of claims that cover about 11,441 hectares to the north and south of Fish Creek. The claims also include the Three Cubs prospect (LH009) and an unnamed prospect (LH010) which may represent similar mineralization. The center of the 2005 drill sites is accurately located about 0.5 mile south-southwest of the center of section 31, T. 19 N., R. 24 W., of the Seward Meridian.
Geology: In 1990 Allen reported anomalous gold in a rock at sample location 819 from a basal moraine at this locality. A GIS compilation and follow-up of published U.S. Geological survey mapping and sampling in the area (Allen, 1990; Allen and others 1990; Allen and Slaughter, 1990) by Kennecott Exploration led to the discovery on the Terra property of finely disseminated native gold and minor sulfides and sulfosalts in tectonic breccias and carbonate-quartz veins in monzonite and diorite intrusive rocks of the Hartman sequence and Jurassic or Lower Cretaceous hornfelsed sedimentary rocks of the Kahiltna terrane (Porterfield, 2000). Porterfield describes two target areas, each approximately 6,000 feet in length, that contain high-grade mineralization in quartz veins--as much as 687 parts per million (ppm) gold and 1,135 ppm silver-- and carbonate-cemented tectonic breccias (as much as 71 ppm gold and 572 ppm silver) that cut intrusive rock and hornfels. Rock-chip samples, talus fines, and soil samples were collected from two target areas on the Terra prospect. Gold assays have a positive correlation with arsenic, silver, antimony, copper, and lead, and Porterfield (2000) reports that bismuth and tungsten are anomalous in some samples. In 2004, AngloGold Ashanti (USA) Exploration, Inc. began work on the Terra prospect with surface geochemistry and outcrop sampling and in 2005, drilled 12 holes south of the terminus of the glacier at the head of Fish Creek. In 2006, International Tower Hill Mines began work on the property in a joint venture with AngloGold; they drilled 12 holes in 2006 and another 15 holes in 2007 (International Tower Hill Mines, Ltd., 2008, Terra). The mineralization at the Terra prospect consists of high-grade epithermal, quartz-carbonate veins 0.1 to 2 meters thick with visible gold. The veins are near the periphery of a Cretaceous diorite stock that intrudes a thick sequence of carbonaceous shale of the Late Jurassic Kahinta Shale. The veins typically contain gold, electrum, sulfosalts, arsenopyrite, pyrite, pyrrhotite, sphalerite, and chalcopyrite. Alteration includes silica-rich selvages near the veins and sericite-rich selvages farther away. The selvages may also contain up to 10 percent pyrite and arsenopyrite but seldom extend more than a meter from the veins. The holes on the Ben Vein indicate that it extends for at least 400 meters along strike to a depth of at least 350 meters. It varies from from 0.2 to 3.0 meters wide and has an average gold value of 19.8 grams per ton. . Five other vein systems have been identified on the prospect including a new discovery in 2007, the Ice vein. All of the vein systems have a north-northwest to north-south strike with with variable west dips. Early in 2008, International Tower Hlll (Klipfel, Paul, 2008) announced an inferred resource estimate for the Ben Vein of 168,000 ounces of gold and 318,000 ounces of silver in ore with an average grade of 12.2 grams of gold per ton and 23.1 grams of silver per ton. The mineralization is open at both ends and at depth.
Workings: Kennecott Exploration carried out reconnaissance mapping and surface sampling in the late 1990's that first identified the Terra deposit (Porterfield, 2000). In 2004, AngloGold Ashanti (USA) Exploration, Inc. (2008) began work on the Terra prospect with surface geochemistry and outcrop sampling, and in 2005 they drilled 12 holes south of the terminus of the glacier at the head of Fish Creek. In 2006, International Tower Hill Mines began work on the property in a joint venture with AngloGold; they drilled 12 holes in 2006 and another 15 holes in 2007.
Age: Cretaceous? Sericite from a quartz vein in hornfels gave an Ar/Ar age date of 66.4 +/- 5.7 Ma (Porterfield, 2000).
Alteration: Carbonate, iron-oxide, quartz, and sericite in selvages near the veins.
Reserves: Early in 2008, International Tower Hlll (2008, Terra) announced an initial inferred resource estimate for the Ben Vein of 168,000 ounces of gold and 318,000 ounces of silver in ore with an average grade of 12.2 grams of gold per ton and 23.1 grams of silver per ton. The mineralization is open at both ends and at depth.

Commodities (Major) - Ag, Au, Cu, Mo,Pb; (Minor) - As, Sb, W
Development Status: None
Deposit Model: Epithermal gold-silver veins.

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Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

ⓘ 'Tennantite Subgroup'

11 valid minerals.