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Portage Mountain Group prospect, Kupreanof Island, Petersburg Borough, Alaska, USAi
Regional Level Types
Portage Mountain Group prospectProspect
Kupreanof IslandIsland
Petersburg BoroughBorough
AlaskaState
USACountry

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Latitude & Longitude (WGS84):
56° 52' 28'' North , 133° 14' 38'' West
Latitude & Longitude (decimal):
Nearest Settlements:
PlacePopulationDistance
Petersburg2,948 (2017)18.8km
Mindat Locality ID:
199474
Long-form identifier:
mindat:1:2:199474:5
GUID (UUID V4):
0


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 Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.


Mineral List


5 valid minerals.

Gallery:

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
Bornite2.BA.15Cu5FeS4
Chalcopyrite2.CB.10aCuFeS2
Pyrite2.EB.05aFeS2
Group 4 - Oxides and Hydroxides
Quartz4.DA.05SiO2
Group 5 - Nitrates and Carbonates
Calcite5.AB.05CaCO3

List of minerals for each chemical element

CCarbon
C CalciteCaCO3
OOxygen
O CalciteCaCO3
O QuartzSiO2
SiSilicon
Si QuartzSiO2
SSulfur
S BorniteCu5FeS4
S ChalcopyriteCuFeS2
S PyriteFeS2
CaCalcium
Ca CalciteCaCO3
FeIron
Fe BorniteCu5FeS4
Fe ChalcopyriteCuFeS2
Fe PyriteFeS2
CuCopper
Cu BorniteCu5FeS4
Cu ChalcopyriteCuFeS2

Other Databases

Link to USGS - Alaska:PE080

Other Regions, Features and Areas containing this locality

North America
North America PlateTectonic Plate
USA

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