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  3. Mineral Resource Data System (MRDS)

Unnamed (near Kohlsaat Peak)

Occurrence in Alaska, United States with commodities Gold, Copper, Molybdenum, Lead, Zinc, Arsenic
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Alteration
  8. Nearby scientific data
  9. Economic information about the deposit and operations
  10. Mining district
  11. Links to other databases
  12. Bibliographic references
  13. Reporter information

Geologic information

Identification information

Deposit ID 10308443
Record type Site
Current site name Unnamed (near Kohlsaat Peak)

Geographic coordinates

Geographic coordinates: -152.73181, 62.2375 (WGS84)
Relative position Curtin, Karlson, O'Leary, Day, and McDougal (1978) locate this silt sample site approximately one and a quarter mile N20E of Kohlsaat Peak in the southwest quarter of Section 23, T. 25 N., R. 19 W., of the Seward Meridian.

Site location context

Political divisions (FIPS codes)

Matanuska-Susitna(Borough)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Talkeetna A-6(quadrangle 1:63,360 scale)

Talkeetna SW(quadrangle 1:100,000 scale)

Talkeetna(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Yentna River(hydrologic unit)

Susitna River(hydrologic accounting unit)

South Central Alaska(hydrologic subregion)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Copper Primary
Molybdenum Primary
Lead Primary
Zinc Critical Primary
Arsenic Critical Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Galena Ore
Pyrite Ore
Quartz Gangue
Tourmaline Gangue

Alteration

  • (Local) Carbonate, chlorite, sericite, and quartz alteration.

Nearby scientific data

(1) g
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = Curtin, Karlson, O'Leary, Day, and McDougal, (1978) recorded a silt anomaly with up to 0.75 ppm gold from a stream draining Kohlsaat Peak. In the late 1980s Cominco American Incorporated (unpublished report) collected rock samples of quartz-sericite-chlorite altered intrusive upstream from the published stream silt site that contained values ranging from 2.43 to 7.96 ppm gold from samples with minor arsenopyrite and chalcopyrite. Foley and others (1997) report six rock samples from the Kohlsaat pluton with maximum values of 14 ppb gold, 4 ppb palladium, and 5 ppb platinum. Reiners and others (1996) describe the Kohlsaat pluton as a concentrically zoned body with a biotite-granite-porphyry core that intruded seriate and porphyritic intermediate composition rocks. The latter include olive-, pyroxene-, and biotite-bearing quartz syenite, quartz monzonite, and monzonite. Lamprophyric mafic and ultramafic rocks that range in composition from peridotite to alkali gabbro and monzonite are found as large xenoliths at the northeastern margin of the pluton. The granite-porphyry core is altered to sericite, quartz, carbonate and tourmaline assemblages, with minor enrichments of copper, gold, lead, molybdenum, and zinc. They have postulated that the composite pluton at Kohlsaat formed from depleted mantle melts that were contaminated during several stages of mafic magma generation by crustal components. The Kohlsaat pluton is one of the larger composite plutons (Tcp) in the Yentna region described by Reed and Nelson (1980). These composite plutons form a 65-km-long curvilinear belt from Mt. Estelle in the south to Cascade Creek in the northeast that primarily intrude Mesozoic marine sedimentary rocks (KJs). Anomalous gold, platinum-group elements, copper, chrome, nickel and arsenic are reported from these plutons (Reed and others, 1978; Reed and Nelson, 1980; Nelson and others 1992; Foley and others, 1997). Gold and platinum group element placers have been worked at sites downstream from these bodies (Mertie, 1919; Cobb, 1973). See TL020, TL023, TL052, and TL005.
  • Age = Late Cretaceous/early Tertiary; mineralization is interpreted to be linked to the Kohsaat pluton which has been determined to be 65.6 +/- 1.9 m.y. old by Reed and Lanphere, 1973.

Economic information about the deposit and operations

Development status Occurrence

Mining district

District name Yentna

Comments on the workings information

  • Workings / Exploration = Reconnaissance mapping, stream silt and rock sampling by the U.S. Geological Survey (Curtin, Karlson, O'Leary, Day, and McDougal, 1978; Reed and Nelson, 1980) and Cominco American Incorporated in the late 1980s (unpublished report) have been done in this vicinity.

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = Foley and others, 1997

Reporter information

Type Date Name Affiliation Comment
Reporter 10-AUG-98 Madelyn A. Millholland Millholland & Associates

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.