Terra

Prospect in Alaska, United States with commodities Silver, Gold, Copper, Molybdenum, Lead, Arsenic, Antimony, Tungsten

Geologic information

Identification information

Deposit ID 10307757
Record type Site
Current site name Terra

Geographic coordinates

Geographic coordinates: -153.68268, 61.75807 (WGS84)
Relative position The Terra prospect is located in the headwaters of the Hartman River at an elevation between 2590 and 7054 feet in sections 6,7,8,13 and 14, T19N, R24W, of the Seward Meridian south of Fish Creek and approximately one mile southwest of the Three Cub occurrence (LH009). The map site is chosen to represent the general area of gold occurrences within the prospect area.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary
Copper Primary
Molybdenum Primary
Lead Primary
Arsenic Secondary
Antimony Secondary
Tungsten Secondary

Comments on the commodity information

  • Gangue = Carbonate

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Galena Ore
Molybdenite Ore
Pyrite Ore
Pyrrhotite Ore
Tennantite Ore
Jordanite Ore
Gold Ore
Quartz Gangue
Sericite Gangue

Alteration

  • (Local) Carbonate, iron-oxide, quartz, and sericite.

Mineral occurrence model information

Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Nearby scientific data

(1) -153.68268, 61.75807

Comments on the geologic information

  • Geologic Description = 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 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 on the Terra property (Porterfield, 2000). Porterfield (2000) describes two target areas, each approximately 6,000 feet in length, that contain high-grade mineralization in quartz veins (as much as 687 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.
  • Age = Cretaceous Sericite from a quartz vein in hornfels gave an Ar/Ar age date of 66.4 +/- 5.7 Ma (Porterfield, 2000).

Economic information

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Active

Mining district

District name McGrath

Comments on the workings information

  • Workings / Exploration = Reconnaissance and prospect mapping by Kennecott Exploration in the late 1990's included surface observation and sampling (Porterfield, 2000).

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF LH010

Bibliographic references

  • Deposit

    Allen, M.S, 1990, Gold anomalies and newly identified gold occurrences in the Lime Hills quadrangle, Alaska , and their association with the Hartman sequence plutons, in Goldfarb, R. J., Nash, J. T., and Stoeser, J. W., eds., Geochemical studies in Alaska by the U.S. Geological Survey, 1989: U.S. Geological Survey Bulletin 1950, p. F1-F16.

  • Deposit

    Allen, M. S., Malcolm, M. J., Motooka, J. M., and Slaughter, K. E., 1990, Geologic description, chemical analyses, and sample locality map for rock samples collected from the eastern part of the Lime Hills quadrangle, Alaska: U.S. Geological Survey Open-File Report 90-69, 49 p..

  • Deposit

    Allen, M.S., and Slaughter, K. E., 1990, Mineralogical data and sample locality map of nonmagnetic, heavy-mineral-concentrate samples collected from the eastern part of the Lime Hills quadrangle, Alaska: U.S. Geological Survey Open-File Report 90-67, 64 p., 1 plate, scale 1:250,000.

  • Deposit

    Porterfield, Ben, 2000, The Terra gold prospect, Alaska Range, Alaska [abs.]: Alaska Miners Association 17th Biennial Conference on Alaska Mining, Abstracts, p. 58-63.

  • Deposit

    Reed, B.L., and Elliott, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-File Report 70-217, 145 p., 1 sheet, scale 1:250,000. (Also published as U.S. Geological Survey Open-File Report 413).

Comments on the references

  • Primary Reference = Porterfield, 2000

General comments

Subject category Comment text
Deposit Model Name = Polymetallic veins (Cox and Singer, 1986, model 22c)

Reporter information

Type Date Name Affiliation Comment
Reporter 27-JUN-01 Madelyn A. Millholland Applied Geology
Reporter 27-JUN-01 Travis L. Hudson Applied Geology