Gold Molybdenum Occurrence, Purple Lake, Annette Island, Ketchikan Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi
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Latitude & Longitude (WGS84):
55° 6' 24'' North , 131° 29' 20'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Metlakatla | 1,405 (2017) | 6.0km |
| Saxman | 417 (2017) | 24.5km |
| Ketchikan | 8,197 (2017) | 28.0km |
Location: This site represents two occurrences: one is on the north shore of Purple Lake about 1.2 miles east-northeast of the head of the trail to the lake from Tamgas Harbor; the other is at an elevation of about 1600 feet on the crest of the east ridge of Purple Mountain, about 1.2 miles from the peak. The occurrences are in section 13, T. 78 S., R. 92 E., of the Copper River Meridian. The map site is at the approximate midpoint between these occurrences. The site corresponds to loc. 43a, b in Karl (1992). The location is accurate within 0.1 mile.
Geology: The country rock at this site is Silurian trondhjemite (Berg, 1972 [I 684]; Berg and others, 1988). The trondhjemite, which locally is sheared, sericitized, and permeated with hydrothermal hematite, was regionally metamorphosed to greenschist grade in Late Cretaceous time. The occurrences are in sheared, hydrothermally altered trondhjemite, and consist of disseminated pyrite, and of pyrite-magnetite veins associated with a 300-foot-wide shear zone. A sample of rusty, altered, granitic rock contained 0.14 ppm Au; a sample of a pyrite-magnetite vein contained 15 ppm Mo (Karl, 1992, loc. 43a, b).
Workings: A sample of rusty, altered, granitic rock contained 0.14 ppm Au; and a sample of a pyrite-magnetite vein contained 15 ppm Mo (Karl, 1992, loc. 43a, b).
Age: Probably Late Cretaceous or younger.
Alteration: Trondhjemite is sericitized and locally permeated with hydrothermal hematite.
Commodities (Major) - Au, Mo
Development Status: None
Deposit Model: Disseminated sulfide and magnetite mineralization of undetermined origin.
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
2 valid minerals.
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 2 - Sulphides and Sulfosalts | |||
|---|---|---|---|
| ⓘ | Pyrite | 2.EB.05a | FeS2 |
| Group 4 - Oxides and Hydroxides | |||
| ⓘ | Magnetite | 4.BB.05 | Fe2+Fe3+2O4 |
List of minerals for each chemical element
| O | Oxygen | |
|---|---|---|
| O | ⓘ Magnetite | Fe2+Fe23+O4 |
| S | Sulfur | |
| S | ⓘ Pyrite | FeS2 |
| Fe | Iron | |
| Fe | ⓘ Magnetite | Fe2+Fe23+O4 |
| Fe | ⓘ Pyrite | FeS2 |
Other Databases
| Link to USGS - Alaska: | KC177 |
|---|
Other Regions, Features and Areas containing this locality
North America
- Coast MountainsMountain Range
North America PlateTectonic Plate
- Alexander DomainDomain
- Alexander TerraneVolcanic Arc
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