Unnamed Occurrence (ARDF - MG088; in saddle between Post River and South Fork), McGrath Mining District, Bethel Census Area, Alaska, USAi
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Latitude & Longitude (WGS84):
62° 0' 50'' North , 153° 26' 31'' West
Latitude & Longitude (decimal):
Köppen climate type:
Location: This unnamed occurrence is located in a saddle between tributaries of the Post River and South Fork of the Kuskokwim River; it is at an elevation of 5,150 feet (1,570 m) in the center of sec. 11, T. 22 N., R. 23 W., of the Seward Meridian. The reporter visited the site in 1988; at station no. 88BT164.
Geology: This unnamed occurrence is a low-sulfide, quartz-carbonate vein or veins intruding a border phase of the 37.9 Ma, Hartman Pluton (Solie and others, 1991; Bundtzen, Harris, and Gilbert, 1997). The border phase consists of very fine-grained biotite-rich granodiorite and monzonite. The border phase is in contact with a massive hornfels aureole that is approximately 125 meters wide. A one meter wide, low sulfide, quartz carbonate vein swarm strikes N70W for about 115 meters through the saddle. The veins cuts the intrusive border phase, but apparently die out in the hornfels aureole. Disseminated arsenopyrite and pyrite grains occur near vein margins. One grab sample of the mineralized vein contained 6,500 ppm arsenic, 71 ppb gold, and 250 ppm antimony.
Workings: The reporter sampled the occurrence during a geologic mapping program for the Alaska Division of Geological and Geophysical Surveys in 1988 (Bundtzen, Harris, and Gilbert, 1997). One grab sample of the mineralized vein contained 6,500 ppm arsenic, 71 ppm gold, and 250 ppm antimony.
Alteration: Secondary biotite (potassic) in the border phase.
Reserves: None.
Commodities (Major) - As; (Minor) - Au, Sb
Development Status: No
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).
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:
| ⓘ Arsenopyrite Formula: FeAsS |
| ⓘ Quartz Formula: SiO2 |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 2 - Sulphides and Sulfosalts | |||
|---|---|---|---|
| ⓘ | Arsenopyrite | 2.EB.20 | FeAsS |
| 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 | ⓘ Arsenopyrite | FeAsS |
| Fe | Iron | |
| Fe | ⓘ Arsenopyrite | FeAsS |
| As | Arsenic | |
| As | ⓘ Arsenopyrite | FeAsS |
Other Databases
| Link to USGS - Alaska: | MG088 |
|---|
Other Regions, Features and Areas containing this locality
North AmericaContinent
North America PlateTectonic Plate
- Farewell buried DomainDomain
- Farewell TerranePassive Margin
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