Omar

Site Name

Primary: Omar

---

Commodity

Primary: Copper
Secondary: Cobalt

---

Location

State: Alaska
District: Kiana

---

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: Kipushi Cu-Pb-Zn (BC name is Carbonate-hosted Cu)

---

Orebody

Not available

---

Structure

Not available

---

Alterations

Alteration Type: L
Alteration Text: Hydrothermal dolomitization.

---

Rocks

Name: Dolomite
Role: Host
Age Type: Host Rock
Age Young: Late Devonian

---

Analytical Data

Not available

---

Materials

Ore: Bornite
Ore: Chalcopyrite
Ore: Covellite
Ore: Malachite
Ore: Pyrite
Ore: Tetrahedrite
Gangue: Calcite
Gangue: Quartz

---

Comments

Comment (Exploration): Status = Active?

Comment (Commodity): Gangue = iron oxides

Comment (Deposit): Model Name = Kipushi Cu-Pb-Zn (Cox and Singer, 1986; model 32c).

Comment (Deposit): Other Comments = Outcrops are rare at Omar and extensive frost-heaved rubble obscures most lithologic contacts.

Comment (Reference): Primary Reference = Degenhart and others, 1978; Folger and Schmidt, 1986

Comment (Reserve-Resource): Reserves = Based on results of two drill holes, Bear Creek Exploration calculated possible reserves of 200,000 tons of ore containing 9% copper.

Comment (Workings): Workings / Exploration = The Omar deposit was discovered by Bear Creek Exploration in 1962 as a result of a regional geochemical reconnaissance program. Work done on the prospect includes geologic mapping, soil, silt and rock sampling, hand trenching, ATM and EM surveys and 19 core drill holes. The geophysical surveys produced indifferent results even though they were run in areas of known mineralization (C.G. Bigelow, personal communication, 1975).

Comment (Geology): Age = Devonian.

Comment (Geology): Geologic Description = The Omar deposit consists of copper and iron sulfides in discordant veinlets, blebs and stringers in Devonian carbonates. A 3-kilometer-long, complex fracture zone trends north northwest across the prospect and hosts the deposit. Highly leached gossans are in the southern and central areas of the prospect. Three samples of gossan contained 1,070 ppm copper, greater than 20,000 ppm copper, and 13,400 ppm copper. Mineralized zones containing chalcopyrite, bornite, covellite and malachite in breccias and fracture fillings range from 300 to 1,000 meters long and up to 30 meters wide. Bornite and chalcopyrite are the dominant copper sulfides. Typical samples of sulfide-bearing talus contain 9.6% Cu. A sample from the southwest slope of hill 2455 contained 15.39% copper; other samples collected along the 3-kilometer trend ranged from 0.1% Cu to 9.6% Cu (Degenhart and others, 1978). High values of cobalt accompany the copper sulfides, along with minor zinc and silver. The thickest intercepts from two drill cores 300 feet apart were 25 to 30 feet of 9% Cu. These holes intersected two parallel shear zones (C.G. Bigelow, personal communication, 1975). ? Microscopic examination shows that the chalcopyrite forms coherent exsolution lamellae and non-coherent blebs and dots within bornite or tetrahedrite. Solution of the host dolostone created open spaces which were filled by dolomite, sulfide and quartz. The mineralizing event occurred prior to metamorphism and deformation associated with the middle Jurassic to Cretaceous Brooks Range orogeny (Folger and Schmidt, 1986). The carbonate sequences at Omar have been folded into broad anticlines and synclines. Most rock units at Omar strike north-northeast to northwest. Dips vary from 6 degrees to vertical. The geologic setting and mineralization at Omar closely resemble those at Ruby Creek, 100 miles to the east in the Ambler quadrangle.

---

References

Reference (Deposit): Degenhart, C.E., Griffis, R.J., McQuat, J.F., and Bigelow, C.G., 1978, Mineral studies of the western Brooks Range performed under contract to the U.S. Bureau of Mines, Contract #JO155089: U.S. Bureau of Mines Open-File Report 103-78, 529 p., 11 sheets.

Reference (Deposit): U.S. Bureau of Land Management, 1989, Geology, Energy and Mineral Resources, Proposed Squirrel River Wild and Scenic River and adjacent area, Baird Mountains, northwest Alaska: U.S. Bureau of Land Management, Division of Mineral Resources, Kobuk District, 42 p.

Reference (Deposit): Cobb, E.H., Mayfield, C.F., and Brosge, W.P., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in eleven quadrangles in northern Alaska (Arctic, Baird Mountains, Chandler Lake, DeLong Mountains, Demarcation Point, Howard Pass, Misheguk Mountain, Mount Michelson, Noatak, Point Lay, and Table Mountain); Supplement to Open-File Report 75-628; Part A, Summaries of data to January 1, 1981: U.S. Geological Survey Open-File Report 81-767-A, 25 p.

Reference (Deposit): WGM Inc., 1980, Non-fuel mineral resource study of Alaska: Anchorage, Alaska, WGM, Inc., unpublished report, 320 p. (Report held by NANA Regional Corporation, Anchorage, Alaska).

Reference (Deposit): Jansons, Uldis, 1982, Cobalt content in samples from the Omar copper prospect, Baird Mountains, Alaska: U.S. Bureau of Mines Open-File Report MLA 109-82, 16 p.

Reference (Deposit): Folger, P.F., and Schmidt, J.M., 1986, Geology of the carbonate-hosted Omar copper prospect, Baird Mountains, Alaska: Economic Geology, v. 81, p. 1690-1695.

Reference (Deposit): Schmidt, J.M., and Folger, P.F., 1986, Lead-zinc-silver mineralization in Paleozoic dolostones, Powdermilk prospect, Baird Mountains B-4 quadrangle: in Bartsch-Winkler, S., and Reed, K.M., eds., Geologic studies in Alaska by the USGS during 1985: U.S. Geological Survey Circular 978, p. 19-21.

---

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.