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Lead Occurrences, Helen Todd Lake, Annette Island, Ketchikan Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi
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Latitude & Longitude (WGS84):
55° 12' 14'' North , 131° 31' 22'' West
Latitude & Longitude (decimal):
Type:
Group of Occurrences
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Metlakatla | 1,405 (2017) | 9.0km |
| Saxman | 417 (2017) | 13.5km |
| Ketchikan | 8,197 (2017) | 17.2km |
Location: This site represents two occurrences at 1000 feet elevation on the hillside west and southwest of Helen Todd Lake. The occurrences are in sections 10 and 11, T. 77 S., R. 92 E., of the Copper River Meridian. They are about 0.4 mile apart, along an unmapped logging road parallel to, and just below, the crestline of a northeast-trending ridge. The map site is approximately midway between the two occurrences. The site corresponds to locs. 28 and 29 in Berg (1972 [I 684]), and to loc. 15a, b in Karl (1992). The location is accurate within about 0.1 mile.
Geology: The country rocks in the area of the site are undivided, metamorphosed Silurian and Ordovician volcanic, sedimentary, and intrusive rocks; and Silurian trondhjemite that intrudes the Silurian and Ordovician rocks (Berg, 1972; Berg and others, 1988). The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. The occurrences are in foliated, sericitized, trondhjemite, and consist of pyrite, magnetite, and galena in sparse calcite veinlets up to 0.25 inch thick and 2-3 inches long (Berg, 1972, locs. 28, 29; Karl, 1992, loc. 15a, b). The sulfide minerals are also widely disseminated in the trondhjemite.
Age: The veins probably are Late Cretaceous or younger.
Alteration: The trondhjemite hostrock is sericitized and contains disseminated sulfide minerals.
Commodities (Major) - Pb
Development Status: None
Deposit Model: Disseminated sulfide and oxide 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
4 valid minerals.
Detailed Mineral List:
| ⓘ Calcite Formula: CaCO3 |
| ⓘ Galena Formula: PbS |
| ⓘ Magnetite Formula: Fe2+Fe3+2O4 |
| ⓘ Pyrite Formula: FeS2 |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 2 - Sulphides and Sulfosalts | |||
|---|---|---|---|
| ⓘ | Galena | 2.CD.10 | PbS |
| ⓘ | Pyrite | 2.EB.05a | FeS2 |
| Group 4 - Oxides and Hydroxides | |||
| ⓘ | Magnetite | 4.BB.05 | Fe2+Fe3+2O4 |
| 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 | ⓘ Magnetite | Fe2+Fe23+O4 |
| S | Sulfur | |
| S | ⓘ Galena | PbS |
| S | ⓘ Pyrite | FeS2 |
| Ca | Calcium | |
| Ca | ⓘ Calcite | CaCO3 |
| Fe | Iron | |
| Fe | ⓘ Magnetite | Fe2+Fe23+O4 |
| Fe | ⓘ Pyrite | FeS2 |
| Pb | Lead | |
| Pb | ⓘ Galena | PbS |
Other Databases
| Link to USGS - Alaska: | KC181 |
|---|
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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