Terra

Mine, Active

Commodities and mineralogy

Main commodities Ag; Au; Cu; Mo; Pb
Other commodities As; Sb; W
Ore minerals arsenopyrite; chalcopyrite; electrum galena; jordanite; molybdenite; native gold; pyrite; pyrrhotite; sphalerite; tennantite
Gangue minerals carbonate; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale LH
Quadrangle map, 1:63,360-scale D-2
Latitude 61.7739
Longitude -153.7027
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Terra prospect is at an elevation of about 5,030 feet, about 8.5 miles southwest of the junction of Fish Creek and the Hartman River. It is about 0.5 mile south of the center of section 31, T. 19 N., R. 24 W., of the Seward Meridian. The location is accurate to within 500 feet.

Geologic setting

Geologic description

In 1990, Allen reported anomalous gold in a rock at sample location 819 from a basal moraine near here. 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 of finely disseminated native gold and minor sulfides and sulfosalts in tectonic breccia 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 and carbonate-cemented tectonic breccia. The quartz veins contained as much as 687 parts per million (ppm) gold and 1,135 ppm silver; the breccia contained as much as 71 ppm gold and 572 ppm silver.
Rock-chip samples, talus fines, and soil samples were collected from two target areas on the Terra prospect. In samples, gold correlates with arsenic, silver, antimony, copper, and lead. 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. In 2005, they drilled 12 holes south of the terminus of the glacier at the head of Fish Creek (Klipfel and Giroux, 2010). 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). In 2010, International Tower Hill signed a joint venture with the Terra Mining Corporation to explore the property (Terra Mining Corp., 2010). In 2010, International Tower Hill formed a new company, Corvus Gold Inc., to take over many of their prospects, including Terra; the joint venture with Terra Mining continued as before and Terra was acquired by WestMountain Gold Corporation in March of 2011.
WestMountain drilled four more holes in 2011 and extended the Ben vein an additional 200 meters; several other veins were also intersected in the drilling in the hanging wall of the Ben vein (WestMountain Gold Corp., 2011). Some notable intercepts were: 1) 0.84 meters that averaged 7.42 grams of gold per tonne and 69.39 grams of silver per tonne, this included 0.31 meter that averaged 15.60 grams of gold per tonne and 138.00 grams of silver per tonne; 2) 0.36 meters that averaged 35.70 grams of gold per tonne and 174 grams of silver per tonne; 3) 5.60 meters that averaged 8.15 grams of gold per tonne and 69.69 grams of silver per tonne; and 4) 0.53 meters that averaged 25.60 grams of gold per tonne and 4.90 grams of silver per tonne.
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 Kahiltna Shale (Klipfel and Giroux, 2010). 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 the selvages seldom extend more than a meter from the veins. The holes on the Ben Vein indicate that it extends for at least 600 meters along strike and persists 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 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 Hill (Klipfel and Giroux, 2008 and 2010) reported an inferred resource estimate for the Ben Vein of 168,000 ounces of gold and 318,000 ounces of silver in material with an average grade of 12.2 grams of gold per ton and 23.1 grams of silver per ton. The mineralization was then open at both ends and at depth.
In 2016, WestMountain Gold Inc. conducted small-scale surface mining and milling operations at Terra but in late summer, a landslide buried the surface bulk-sampling area. By mid-September, WestMountain Gold Inc. had processed 890 tons of material from the high-grade gold vein at Terra, and had another 1,470 tons of stockpiled material that was mined prior to the landslide (Athey and Werdon, 2017).
Geologic map unit (-153.704943094298, 61.7732610546365)
Mineral deposit model Epithermal gold-silver veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Cretaceous; sericite from a quartz vein in hornfels has an Ar/Ar age date of 66.4 +/- 5.7 Ma (Porterfield, 2000).
Alteration of deposit Carbonates, iron-oxides, quartz, and sericite in selvages near the veins (Klipfel and Giroux, 2008).

Production and reserves

Workings or exploration
Kennecott Exploration carried out reconnaissance mapping and surface sampling in the late 1990s 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; 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. In 2010, International Tower Hill signed a joint venture with the Terra Mining Corporation to explore the property (Terra Mining Corp., 2010). In 2010, International Tower Hill formed a new company, Corvus Gold Inc., to take over many of their prospect, including Terra. The joint venture with Terra Mining continued as before and Terra was acquired by WestMountain Gold Corporation in March of 2011.
WestMountain Gold, Inc. (WMTN) drilled four more holes in 2011. In 2012, WMTN drilled four more holes; in 2013, WMTN drilled five more holes (Greg Schifrin, written communication, 2014).
Indication of production None
Reserve estimates
Early in 2008, International Tower Hill (Klipfel and Giroux, 2010) 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.
In 2013, the first t test run on production occurred 75 tons were run averaging 3 oz per ton (Greg Schifrin, written commun., 2014).
Production notes In 2016, WestMountain Gold Inc. conducted small-scale surface mining and milling operations at Terra but in late summer, a landslide buried the surface bulk-sampling area. By mid-September, WestMountain Gold Inc. had processed 890 tons of material from the high-grade gold vein at Terra, and had another 1,470 tons of stockpiled material that was mined prior to the landslide (Athey and Werdon, 2017).

Additional comments

In 2013, Gustavson and Associates completed a 43-101 report with an indicated resource of 50,000 Au and inferred 370,000 ounces of gold for a total gold resource of 420,000 grade gold and 15.5 grams per ton with a 5 year reserve (WestMountain Gold, Inc., 2014).
In 2014, WMTN acquired 100 percent ownership - buying out Corvus Gold joint venture agreement (WestMountain Gold, Inc., 2014).

References

References

International Tower Hill Mines, Ltd., 2008, Terra: http://www.ithmines.com/s/Terra.asp (as of March 4, 2008).
Klipfel, Paul, 2008, Summary report on the Terra gold project, McGrath district, Alaska: Unpublished report for International Tower Hill Mines, Ltd. (posted on www.sedar.com, February 14, 2008), http://www.sedar.com/GetFile.do?lang=EN&docClass=24&issuerNo=00005628&fileName=/csfsprod/data86/filings/01214217/00000002/C%3A%5CSEDAR%5CFILINGS%5CITH%5CTerra-43-101-Res-Rpt-feb0108.pdf (as of December 1, 2014).
Klipfel, Paul, and Giroux, Gary, 2010, Summary report on the Terra gold project, McGrath district, Alaska: Unpublished report for International Tower Hill Mines Ltd., 71 p. (posted on www.sedar.com, July 15, 2010), http://www.sedar.com/GetFile.do?lang=EN&docClass=24&issuerNo=00005628&fileName=/csfsprod/data109/filings/01607187/00000002/m%3A%5CG_drive%5CDMA%5CV31429%5Carrangmt%5Cterra.pdf (as of December 1, 2014).
Porterfield, Ben, 2000, The Terra gold prospect, Alaska Range, Alaska [abs.]: Alaska Miners Association 17th Biennial Conference on Alaska Mining, Abstracts, p.58-63.
Terra Mining Corp., 2010, Corvus Gold Inc. signs definitive joint venture agreement for the development high grade Terra gold project, Alaska: http://www.terraminingcorp.com/news.html (News release, Oct. 6, 2010).
WestMountain Gold Corp., 2011, Drilling at Ben Vein intersects 3.4m @11.6 g/t gold at Terra project, Alaska: http://terraminingcorp.com/site/drilling-at-ben-vein-intersects-3-4m-11-6-gt-gold-at-terra-project-alaska/ (News release, December 6, 2011).
WestMountain Gold Corp., 2014, Terra Project Overview: http://www.westmountaingold.com/index.php?option=com_content&view=article&id=52&Itemid=118 (as of December 9, 2014).
Reporters Travis L. Hudson (Applied Geology) and Madelyn A. Millholland (Millholland & Associates); D.J. Grybeck (Contractor, USGS); V.C. Zinno (Alaska Earth Sciences, Inc.); M.B. Werdon (DGGS)
Last report date 8/26/2017