Myghapowit Mountain Prospect, Bering Sea Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Myghapowit Mountain Prospect	Prospect
Bering Sea Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: This site is a local upland on the east side of Myahapowit Mountain between the headwaters of the Seknak and Maknek Rivers (east central St. Lawrence Island). It is a conspicuous orange-weathering area over 1 mile across. It was not included by Cobb (1972; 1980).
Geology: The 2 square mile, highly altered quatrz latite and latite stock is intruded along the east side of the Myghapowit pluton in east central St. Lawrence Island (Patton and Csejtey, 1971; Patton and Csejtey, 1980). About 1 mile of the northwest contact is with Mississippian limestone (Patton and Csejtey, 1971, Figure 3). The stock is altered to an assemblage of sericite, chlorite, clay minerals, and secondary silica. Only traces of the original textures are preserved in most places but breccia textures characterize several samples from the area (Patton and Csejtey, 1971, Table 1). The altered rocks are highly oxidized and well developed limonite staining and veining makes the stock conspicuously visible from a distance due to its red and orange color. Pyrite is the only sulfide mineral that has been identified in hand specimens. Fifteen grab samples of rocks and soils from the altered stock have low to moderately anomalous contents of several metals but most importantly show that gold is present in this mineralized system. All of the samples had detectable gold although only three were at levels at or above the 0.02 ppm dectection limit (0.2, 0.3. and 0.6 ppm, Patton and Csejtey, 1971, Table 1). One of these samples contained 3,000 ppm arsenic and 300 ppm antimony. In the fifteen samples, lead ranges from 30 to 3,000 ppm, copper from 5 to 150 ppm, molydenum from less than 5 to 700 ppm, bismuth from less than 10 to 300 ppm, tin from less than 10 to 150 ppm, and silver from less than 0.5 to 1 ppm. Three stream sediment samples, each from the upper part of a drainage headed against the altered stock, contain 150 ppm lead and 10 to 20 ppm molybdenum (Patton and Csejtey, 1972). Other elements were not anomalous in these stream sediment samples.
Workings: Fifteen grab samples of rocks and soils from the altered stock have low to moderately anomalous contents of several metals but most importantly show that gold is present in this mineralized system. All of the samples had detectable gold although only three were at levels at or above the 0.02 ppm dectection limit (0.2, 0.3. and 0.6 ppm, Patton and Csejtey, 1971, Table 1). One of these samples contained 3,000 ppm arsenic and 300 ppm antimony. In the fifteen samples, lead ranges from 30 to 3,000 ppm, copper from 5 to 150 ppm, molydenum from less than 5 to 700 ppm, bismuth from less than 10 to 300 ppm, tin from less than 10 to 150 ppm, and silver from less than 0.5 to 1 ppm. Three stream sediment samples, each from the upper part of a drainage headed against the altered stock, contain 150 ppm lead and 10 to 20 ppm molybdenum (Patton and Csejtey, 1972). Other elements were not anomalous in these stream sediment samples.
Age: Patton and Csejtey (1980) indicate that the altered stock is Cretaceous or Tertiary. There is no age control other than that it appears to intrude the Myghapowit pluton (mid-Cretaceous) and Mississippian limestone (Patton and Csejetey, 1980).
Alteration: The stock is altered to an assemblage of sericite, chlorite, clay minerals, and secondary silica. Only traces of the original textures are preserved in most places but breccia textures characterize several samples from the area (Patton and Csejtey, 1971, Table 1). The altered rocks are highly oxidized and well developed limonite staining and veining makes the stock conspicuously visible from a distance due to its red and orange color.

Commodities (Major) - Au; (Minor) - Ag, Pb
Development Status: None
Deposit Model: Gold in altered, hypabyssal, felsic intrusive rocks.

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Link to USGS - Alaska:	SL021

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References