Moghoweyik R.

Occurrence, Inactive

Alternative names

Upper

Commodities and mineralogy

Main commodities Mo
Other commodities Cu
Ore minerals molybdenite
Gangue minerals quartz; pyrite

Geographic location

Quadrangle map, 1:250,000-scale SL
Quadrangle map, 1:63,360-scale C-6
Latitude 63.45
Longitude -171.61
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is in the headwaters of the Moghoeyik River on western St. Lawrence Island. The mineralized area is a 1/2 mile wide zone in the eastern part of the Sevuokuk pluton near its contact with volcanic rocks. The site is located within 1/2 mile and is locality 5 of Cobb (1972). Cobb (1980) summarized relevant references under the name 'Moghoeyik R., upper'.

Geologic setting

Geologic description

Molybdenite is sparsely distributed throughout a 1/2 mile wide zone in the eastern part of the Sevuokuk pluton near the contact with Cretaceous volcanic rocks. The Sevuokuk pluton is a mid-Cretaceous (108 +/- 3.2 Ma) composite body that includes biotite hornblende quartz monzonite and biotite quartz monzonite phases (Csejtey, Patton, and Miller, 1971; Patton and Csejtey, 1980). Here, pyritiferous and highly oxidized biotite quartz monzonite is cut by quartz veins and locally silicified. Molybdenite occurs as scales on fractures, in thin veinlets, and as large euhedral crystals in drusy quartz veins (Patton and Csejtey, 1971, p. C11). Three grab samples contained 500, 500, and 7 ppm molybdenum and 20, 150, and 1,000 ppm copper respectively (Patton and Csejtey, 1971, p. C8). Four stream sediment samples from the drainage headwatered in this mineralized area (Patton and Csejtey, 1972) contained only weakly anomalous concentrations of molybdenum (to 15 ppm) and copper (to 200 ppm).
Geologic map unit (-171.612779233664, 63.4490703709182)
Mineral deposit model Porphyry Mo, low-F? (Cox and Singer, 1986; model 21b?).
Mineral deposit model number 21b?
Age of mineralization Mid-Cretaceous, the age of the host Sevuokuk pluton (108 +/- 3.2 Ma; Patton and Csejtey, 1980).
Alteration of deposit The biotite quartz monzonite is pyritized, cut by some quartz veins, and locally silicified. It is heavily oxidized and stained with limonite. Other alteration is probably present.

Production and reserves

Workings or exploration Three grab samples contained 500, 500, and 7 ppm molybdenum and 20, 150, and 1,000 ppm copper respectively (Patton and Csejtey, 1971, p. C8). Four stream sediment samples from the drainage headwatered in this mineralized area (Patton and Csejtey, 1972) contained only weakly anomalous concentrations of molybdenum (to 15 ppm) and copper (to 200 ppm).
Indication of production None

References