Portage Mountain Group prospect, Kupreanof Island, Petersburg Borough, Alaska, USAi
| Regional Level Types | |
|---|---|
| Portage Mountain Group prospect | Prospect |
| Kupreanof Island | Island |
| Petersburg Borough | Borough |
| Alaska | State |
| USA | Country |
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Latitude & Longitude (WGS84):
56° 52' 28'' North , 133° 14' 38'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Petersburg | 2,948 (2017) | 18.8km |
This prospect is now in the Petersburg Creek-Duncan Salt Chuck Wilderness which is closed to mineral exploration and mining. Some recent U.S. Geological Survey publications including Cobb (1978) Cobb (1972), Berg and Cobb (1967), and an earlier generation of ARDF probably combine two different prospects on the west side of Portage Mountain that are described separately in ARDF as this prospect and PE 009.
Location: There is some confusion in the old literature about the location and geology of two prospects in the area between Portage Mountain and the North Arm of Duncan Canal. Still and others (2002) spent considerable time in the field and library trying to decipher their location and descriptions. They concluded that the Portage Mountain Group consisted of 4 quartz-calcite veins that are at an elevation of between 2,000 and 3,000 feet on the west side of Portage Mountain. They could not find the old workings that they think are in the NE 1/4, NW 1/4, section 2, T. 58 S., R. 77 E. The coordinates above reflect their preferred location (The other prospect is the Silver Star prospect which consists of hornblendite with sulfides is at an elevation of about 400 feet, about 1.6 mile west-southwest of Duncan Peak; it is ARDF PE009.)
Geology: As described by Wright and Wright (1905, 1908) and Roehm (1945), the deposit consists of four, thin northeast-striking quartz-calcite veins with pyrite, pyrrhotite, chalcopyrite, bornite, and tetrahedrite. Samples of the veins contained up to 0.4 ounce of gold per ton and 2 ounces of silver per ton. The rocks have been variously mapped as metasedimentary rocks of the Jurassic to Cretaceous Seymour Canal Group by Karl and others (1999) or Cretaceous Stephens Passage Group by Brew (1997) that have been intruded by Cretaceous diorite. Roehm (1945) noted that the workings included a 130-foot adit and open cuts. However, Still and others (2002) could not locate the prospect in spite of a diligent search.
Workings: Roehm (1945) noted that the workings included a 130-foot adit and open cuts. However, Still and others (2002) could not locate the prospect in spite of a diligent search.
Age: Too little evidence to determine.
Commodities (Major) - Ag, Au, Cu
Development Status: None
Deposit Model: Polymetallic quartz-calcite veins.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsCommodity List
This is a list of exploitable or exploited mineral commodities recorded at this locality.Mineral List
5 valid minerals.
Detailed Mineral List:
| ⓘ Bornite Formula: Cu5FeS4 |
| ⓘ Calcite Formula: CaCO3 |
| ⓘ Chalcopyrite Formula: CuFeS2 |
| ⓘ Pyrite Formula: FeS2 |
| ⓘ Quartz Formula: SiO2 |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 2 - Sulphides and Sulfosalts | |||
|---|---|---|---|
| ⓘ | Bornite | 2.BA.15 | Cu5FeS4 |
| ⓘ | Chalcopyrite | 2.CB.10a | CuFeS2 |
| ⓘ | Pyrite | 2.EB.05a | FeS2 |
| Group 4 - Oxides and Hydroxides | |||
| ⓘ | Quartz | 4.DA.05 | SiO2 |
| Group 5 - Nitrates and Carbonates | |||
| ⓘ | Calcite | 5.AB.05 | CaCO3 |
List of minerals for each chemical element
| C | Carbon | |
|---|---|---|
| C | ⓘ Calcite | CaCO3 |
| O | Oxygen | |
| O | ⓘ Calcite | CaCO3 |
| O | ⓘ Quartz | SiO2 |
| Si | Silicon | |
| Si | ⓘ Quartz | SiO2 |
| S | Sulfur | |
| S | ⓘ Bornite | Cu5FeS4 |
| S | ⓘ Chalcopyrite | CuFeS2 |
| S | ⓘ Pyrite | FeS2 |
| Ca | Calcium | |
| Ca | ⓘ Calcite | CaCO3 |
| Fe | Iron | |
| Fe | ⓘ Bornite | Cu5FeS4 |
| Fe | ⓘ Chalcopyrite | CuFeS2 |
| Fe | ⓘ Pyrite | FeS2 |
| Cu | Copper | |
| Cu | ⓘ Bornite | Cu5FeS4 |
| Cu | ⓘ Chalcopyrite | CuFeS2 |
Other Databases
| Link to USGS - Alaska: | PE080 |
|---|
Other Regions, Features and Areas containing this locality
North America
- Coast MountainsMountain Range
North America PlateTectonic Plate
- Alexander DomainDomain
- Alexander TerraneVolcanic Arc
USA
- Alaska
- Petersburg Borough
- Kupreanof Mining DistrictMining District
- ⭔Wrangell-Petersburg Census AreaBorough
- Petersburg Borough
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References
Wright, Fred Eugene; Wright, Charles Will (1908) The Ketchikan and Wrangell mining districts, Alaska. U.S. Geological Survey Bulletin B 347. U.S. Geological Survey 210 pp.
Roehm, J. C. (1945) Preliminary report of investigations and itinerary of J.C. Roehm in the Wrangell and Petersburg precincts, Alaska. Alaska Territorial Department of Mines Itinerary Report IR 195-37. Alaska Territorial Department of Mine 13 pp.
Berg, Henry C.; Cobb, E.H. (1967) Metalliferous Lode Deposits of Alaska. Geological Survey Bulletin 1246. US Geological Survey 254 pp.