Tarasof Point Occurrence, Aleutians Mining District, Aleutians West Census Area, Alaska, USAi
Regional Level Types | |
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Tarasof Point Occurrence | Occurrence |
Aleutians Mining District | Mining District |
Aleutians West Census Area | Census Area |
Alaska | State |
USA | Country |
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Latitude & Longitude (WGS84):
53° 40' 59'' North , 166° 55' 58'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
Place | Population | Distance |
---|---|---|
Unalaska | 4,491 (2017) | 33.5km |
Dutch Harbor | 4,376 (2018) | 34.4km |
Mindat Locality ID:
200294
Long-form identifier:
mindat:1:2:200294:4
GUID (UUID V4):
c59d5fae-3509-4743-b01f-9cf1e2f726ca
The mode of occurrence suggests an epithermal gold vein model should be considered as a possible model for this system.
Location: West side of Anderson Bay, 2 miles (3.2 km) southwest of Tarasof Point. Anomaly no. 20 of Christie (1974). Anderson Bay is the south arm of Makushin Bay.
Geology: The occurrence is defined by multiple color anomalies surrounding breccia pipes emplaced through a pendant(?) of volcanic rocks of the Unalaska Formation (see Drewes and others, 1961) between exposures of diorite plutons. The color anomalies occur in two 1,000 ft (300 m) by 3,000 ft (915 m) areas. Late mineral quartz-feldspar porphyry and crowded feldspar porphyry dikes cut the breccia pipes. The breccia pipes may have originally contained up to 15 to 20 percent sulfides, which are now totally leached. Copper may have been present, as traces of chalcopyrite occur in the adjacent diorite plutons. Alteration and the amount of pyrite appear to decrease abruptly away from areas of breccia. According to Christie (1974), fracturing is very important (in localizing alteration?). Within the breccia pipes, there is intense silicification and peripheral to this, secondary chlorite and epidote are developed. The occurrence is capped by highly altered rocks distinguished by the development of limonite.
Workings: Reconnaissance mapping and multiple soil samples were used to evaluate the color anomaly. Samples showed up to 260 ppm copper, 28 ppm molybdenum, 2.6 ppm silver, and 0.24 ppm gold.
Age: Cenozoic
Alteration: The core of the occurrence shows intense silicification and on the periphery, the development of chlorite and epidote indicate propylitic alteration. Leaching is complete in the area of interest.
Commodities (Major) - Mo, Cu, Ag, Au
Development Status: No
Deposit Model: Copper porphyry, epithermal gold vein
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.
Detailed Mineral List:
ⓘ 'Chlorite Group' |
ⓘ Epidote Formula: (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH) |
ⓘ 'Limonite' |
ⓘ Pyrite Formula: FeS2 |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
Group 2 - Sulphides and Sulfosalts | |||
---|---|---|---|
ⓘ | Pyrite | 2.EB.05a | FeS2 |
Group 9 - Silicates | |||
ⓘ | Epidote | 9.BG.05a | (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH) |
Unclassified | |||
ⓘ | 'Chlorite Group' | - | |
ⓘ | 'Limonite' | - |
List of minerals for each chemical element
H | Hydrogen | |
---|---|---|
H | ⓘ Epidote | (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH) |
O | Oxygen | |
O | ⓘ Epidote | (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH) |
Al | Aluminium | |
Al | ⓘ Epidote | (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH) |
Si | Silicon | |
Si | ⓘ Epidote | (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH) |
S | Sulfur | |
S | ⓘ Pyrite | FeS2 |
Ca | Calcium | |
Ca | ⓘ Epidote | (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH) |
Fe | Iron | |
Fe | ⓘ Epidote | (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH) |
Fe | ⓘ Pyrite | FeS2 |
Other Databases
Link to USGS - Alaska: | UN027 |
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