Koyana Creek

Site Name

Primary: Koyana Creek

---

Commodity

Primary: Gold

---

Location

State: Alaska
District: Council

---

Land Status

Not available

---

Holdings

Not available

---

Workings

Not available

---

Ownership

Not available

---

Production

Not available

---

Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

---

Physiography

Not available

---

Mineral Deposit Model

Model Name: Low-sulfide Au-quartz vein

---

Orebody

Not available

---

Structure

Not available

---

Alterations

Alteration Type: L
Alteration Text: Quartz veining and sulfide dissemination; oxidation is probably present although not described. At the nearby Saddle prospect (SO175), alteration minerals in the host schist include plagioclase, chlorite, carbonate, white mica, biotite, titanite, and tourmaline.

---

Rocks

Not available

---

Analytical Data

Not available

---

Materials

Ore: Gold
Ore: Arsenopyrite
Gangue: Quartz

---

Comments

Comment (Exploration): Status = Active?

Comment (Workings): Workings / Exploration = Three short adits and a shallow shaft are noted in the area (Mulligan, 1971). One of the adits was 30-feet long (Cathcart, 1922).

Comment (Geology): Age = Mid-Cretaceous; white mica from quartz veins in the Koyana Creek area gave Ar/Ar plateau dates of 109.1 +/- 0.7 Ma and 109.6 +/- 0.2 Ma (Ford and Snee, 1996).

Comment (Production): Production Notes = A few tons of ore were reported to have been sacked but it is not known if this was shipped (Smith and Eakin, 1911).

Comment (Reference): Primary Reference = Herried, 1965

Comment (Deposit): Model Name = Discontinuous, irregular to joint-contolled quartz veins and veinlets with dissemminated arsenopyrite and pyrite in metasedimentary schist; low sulfide-Au quartz vein (Cox and Singer, 1986; model 36a).

Comment (Geology): Geologic Description = Metasedimentary schist intercalated in Paleozoic marble forms the bedrock of lower Koyana Creek and exposures along the coast for several hundred feet east of its mouth. Gold-bearing mineralization was prospected here in the early 1900's (Collier and others, 1908). Three short adits and a shallow shaft were developed (Mulligan, 1971). Exposures at the face of a 30-foot-long adit showed an 8-inch-wide quartz vein, a foot-wide iron-stained gouge zone along the vein, and an arsenopyrite and pyrite in the vein and enclosing schist (Cathcart, 1922). The schist contains quartz segregations and boudins with oxidized iron-stained spots in addition to crosscutting, at least partly joint-controlled, quartz veins and veinlets. The latter locally contain both pyrite and arsenopyrite (Herried, 1965). The largest crosscutting quartz vein observed by Herried (1965) was 4 inches wide and 10 feet long. Seven grab and chip samples from this area contained 0.01 to 0.32 ounces Au per ton and 0.16 to 0.65 ounces Ag per ton (Herried, 1965). One composite chip sample of schist, collected every 10 feet over a distance of 700 feet, contained 0.07 ounces Au per ton. This prospect if probably similar to the nearby Saddle prospect (SO175). The Saddle prospect is known from the work of Ford (1993) and Ford and Snee (1996). A large gold and arsenic anomaly in soils led to its discovery. Gold-bearing quartz veins are localized in extensional joints in quartz-muscovite schist that strike easterly and dip moderately to the south. The veins are discontinuous and commonly less than 3 inches thick. Gold grades are irregularly distributed; vein intersections up to 3.3 feet across have contained up to 1.8 ounces Au per ton. Minerals identified in the veins include arsenopyrite, biotite, carbonate, chlorite, fluorite, marcasite, plagioclase, pyrite, pyrrhotite, quartz, titanite, and white mica. Alteration minerals in the host schist include plagioclase, chlorite, carbonate, white mica, biotite, titanite, and tourmaline. The white mica in the veins is muscovite and that in the host schist is phengite. A sample of vein white mica gave a Ar/Ar plateau age of 109.3 +/- 0.3 Ma and metamorphic white mica in the host schist gave Ar/Ar plateau ages of 122.6 +/- 0.4 Ma and 122.4 +/- 0.2 Ma (Ford and Snee, 1996). The host schist is similar to that at the nearby Bluff (SO135) and Swede Creek (SO133) lode prospects. This schist is a band intercalated in Paleozoic marble (Herried, 1965; Mulligan, 1971; Till and others, 1986). . This deposit is also probably mid-Cretaceous, the age of some other lode gold deposits on southern Seward Peninsula. The southern Seward Peninsula lode gold deposits formed as a result of mid-Cretaceous metamorphism (Apodoca, 1994; Ford, 1993, Ford and Snee, 1996; Goldfarb and others, 1997) that accompanied regional extension (Miller and Hudson, 1991) and crustal melting (Hudson, 1994). This higher temperature metamorphism was superimposed on high pressure/low temperature metamorphic rocks of the region.

---

References

Reference (Deposit): Cathcart, S.H., 1922, Metalliferous lodes in southern Seward Peninsula: U.S. Geological Survey Bulletin 722, p. 163-261.

Reference (Deposit): Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska: Economic Geology Monograph 9, 482 p.

Reference (Deposit): Collier, A. J., Hess, F.L., Smith, P.S., and Brooks, A.H., 1908, The gold placers of parts of Seward Peninsula, Alaska, including the Nome, Council, Kougarok, Port Clarence, and Goodhope precincts: U.S. Geological Survey Bulletin 328, 343 p.

Reference (Deposit): Ford, R.C., and Snee, L.W., 1996, 40Ar/39Ar thermochronology of white mica from the Nome district, Alaska: The first ages of lode sources to placer gold deposits in the Seward Peninsula: Economic Geology, v. 91, p. 213-220.

Reference (Deposit): Miller, E.L., and Hudson, T.L., 1991, Mid-Cretaceous extensional fragmentation of a Jurassic-Early Cretaceous compressional orogen, Alaska: Tectonics, v. 10, p. 781-796.

Reference (Deposit): Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Solomon quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-181, 185 p.

Reference (Deposit): Hudson, T.L. 1994, Crustal melting events in Alaska, in Plafker, G., and Berg, H. C., eds., The Geology of Alaska: Boulder, Colorado, Geological Society of America, The Geology of North America, v. G-1, p. 657-670.

Reference (Deposit): Mulligan, J.J., 1971, Sampling gold lode deposits, Bluff, Seward Peninsula, Alaska, with a section on petrography by Walter L. Gnagy: U.S. Bureau of Mines Report of Investigations 7555, 40 p.

Reference (Deposit): Till, A.B., Dumoulin, J.A., Gamble, B. ., Kaufman, D.S., and Carroll, P.I., 1986, Preliminary geologic map and fossil data, Soloman, Bendeleben, and southern Kotzebue quadrangles, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 86-276, 10 p., 3 plates, scale 1:250,000.

Reference (Deposit): Smith, P.S. and Eakin, H.M., 1911, Mineral resources of Alaska 1910: U.S. Geological Survey Bulletin 480, 333 p..

Reference (Deposit): Ford, R.C., 1993, Geology, geochemistry, and age of gold lodes at Bluff and Mt. Distin, Seward Peninsula, Alaska: Golden, Colorado School of Mines, Ph.D. dissertation, 302 p.

Reference (Deposit): Herreid, G.H., 1965, Geology of the Bluff area, Solomon quadrangle, Seward Peninsula, Alaska: Alaska Division of Geological and Geophysical Surveys Geological Report 10, 21 p., 1 sheet, scale 1:40,000.

Reference (Deposit): Apodoca, L. E., 1994, Genesis of lode gold deposits of the Rock Creek area, Nome mining district, Seward Peninsula, Alaska: Boulder, Colorado, University of Colorado, Ph.D. dissertation, 208 p.

Reference (Deposit): Cobb, E.H., 1972, Metallic resources map of the Solomon quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-445, scale 1:250,000.

---

The Top Ten Gold Producing States

These ten states contributed the most to the gold production that built the West from 1848 through the 1930s. The Top Ten Gold Producing States.