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Gold Silver Occurrence, Purple Lake, Annette Island, Ketchikan Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi
| Regional Level Types | |
|---|---|
| Gold Silver Occurrence | Occurrence |
| Purple Lake | Lake |
| Annette Island | Island |
| Ketchikan Mining District | Mining District |
| Prince of Wales-Hyder Census Area | Census Area |
| Alaska | State |
| USA | Country |
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Latitude & Longitude (WGS84):
55° 5' 41'' North , 131° 32' 5'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Metlakatla | 1,405 (2017) | 4.5km |
| Saxman | 417 (2017) | 25.1km |
| Ketchikan | 8,197 (2017) | 28.3km |
Location: This occurrence is at an elevation of about 500 feet, midway between the northeast head of Tamgas Harbor and the foot of Purple Lake. The site is in section 22 T. 78 S., R. 92 E., of the Copper River Meridian. It corresponds to loc. 45 in Karl (1972). The location, which is erroneously marked as a mine on the Ketchikan A-5 topographic map (1955 ed., revised 1962), is accurate to within about a hundred feet.
Geology: The country rock at this site is Silurian trondhjemite (Berg, 1972 [I 684]; Berg and others, 1988). It was regionally metamorphosed to greenschist grade in Late Cretaceous time, and locally is intensely sheared, sericitized, and permeated with hydrothermal hematite. The occurrence consists of unspecified disseminated sulfide minerals in aplite dikes that cut altered trondhjemite. A sample of the sulfide-bearing aplite contained 0.25 ppm Au, 1.5 ppm Ag, 1000 ppm Cu, and 50 ppm Mo (Karl, 1992, loc. 45). If the aplite dikes postdate the Late Cretaceous regional metamorphism, the mineralization may be Tertiary in age.
Workings: A sample of the sulfide-bearing aplite contained 0.25 ppm Au, 1.5 ppm Ag, 1000 ppm Cu, and 50 ppm Mo (Karl, 1992, loc. 45).
Age: If the aplite dikes postdate the Late Cretaceous regional metamorphism, the mineralization may be Tertiary in age.
Alteration: The trondhjemite locally is sericitized and permeated with hydrothermal hematite. The aplite dikes may postdate this alteration.
Commodities (Major) - Ag, Au, Cu, Mo
Development Status: None
Deposit Model: Disseminated sulfide mineralization of undetermined origin.
Commodity List
This is a list of exploitable or exploited mineral commodities recorded at this locality.List of minerals for each chemical element
Other Databases
| Link to USGS - Alaska: | KC179 |
|---|
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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