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Portland Prospect, Juneau Mining District, Juneau, Alaska, USAi
| Regional Level Types | |
|---|---|
| Portland Prospect | Prospect |
| Juneau Mining District | Mining District |
| Juneau | City Borough |
| Alaska | State |
| USA | Country |
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Latitude & Longitude (WGS84):
58° 15' 15'' North , 134° 21' 3'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Juneau | 32,756 (2017) | 6.7km |
Location: The Portland prospect is at an elevation of approximately 200 feet on Douglas Island, on the southwest side of Gastineau Channel, and about 0.2 mile west-northwest of the mouth of Ready Bullion Creek. It is near the center of the SE1/4 section 6, T. 42 S., R. 68 E. of the Copper River Meridian. The location is accurate.
Geology: The Portland prospect was discovered before 1890 and was developed by a 118-foot adit, a 19-foot adit, and several trenches. The host rocks are black phyllite, green chlorite phyllite and amphibolite (Redman and others, 1989). The black phyllite has been intruded by two, altered, albite-diorite sills that contain quartz and disseminated pyrite. The phyllite contains disseminated pyrite and is silicified along the contact with the amphibolite. U.S. Bureau of Mines samples did not contain significant precious metal values, however a quartz sample from the amphibolite contained 164 ppm percent molybdenum (Redman and others, 1989). The rocks in the general area are Upper Jurassic or Cretaceous marine argillite and graywacke, interbedded with andesite or basalt (Brew and Ford, 1985). The bedded rocks are regionally metamorphosed to prehnite-pumpellyite or greenschist grade, and cut by diorite or gabbro dikes and sills.
Workings: The Portland prospect was discovered before 1890 and was developed by a 118-foot adit, a 19-foot adit, and several trenches.
Alteration: Altered albite-diorite sills.
Commodities (Major) - Au; (Minor) - Mo
Development Status: None
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 | |||
| ⓘ | Quartz | 4.DA.05 | SiO2 |
List of minerals for each chemical element
| O | Oxygen | |
|---|---|---|
| O | ⓘ Quartz | SiO2 |
| Si | Silicon | |
| Si | ⓘ Quartz | SiO2 |
| S | Sulfur | |
| S | ⓘ Pyrite | FeS2 |
| Fe | Iron | |
| Fe | ⓘ Pyrite | FeS2 |
Other Databases
| Link to USGS - Alaska: | JU210 |
|---|
Other Regions, Features and Areas containing this locality
North AmericaContinent
- Coast MountainsMountain Range
North America PlateTectonic Plate
- Taku DomainDomain
- Yukon-TananaVolcanic Arc
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