Moghoweyik R.; Upper Occurrence, Bering Sea Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Moghoweyik R.; Upper Occurrence	Occurrence
Bering Sea Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: 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 fo 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'.
Geology: 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).
Workings: 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).
Age: Mid-Cretaceous, the age of the host Sevuokuk pluton (108 +/- 3.2 Ma; Patton and Csejtey, 1980).
Alteration: 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.

Commodities (Major) - Mo; (Minor) - Cu
Development Status: None
Deposit Model: Fracture fillings, veins, and disseminations of molybdenite in granitic rock. D

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Link to USGS - Alaska:	SL009

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References