308 Zone

Prospect, Active

Commodities and mineralogy

Main commodities Au; Cu; Mo
Ore minerals chalcopyrite; molybdenite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale IL
Quadrangle map, 1:63,360-scale D-7
Latitude 59.7779
Longitude -155.485
Nearby scientific data Find additional scientific data near this location
Location and accuracy The 308 Zone prospect is about 2.8 miles west of the top of Sharp Mountain, near the northeast corner of section 1, T. 5 S., R. 37 W. The location is accurate.

Geologic setting

Geologic description

A single hole was drilled on the 308 Zone in 2004 by Northern Dynasty Minerals Inc. to test a IP geophysical anomaly in an area where a monzodiorite dike projects from the Kaskanak batholith into an area of well-bedded hornfelsed, Jurassic to Cretaceous argillite and siltstone (Rebagliati and Payne, 2005). The hole was entirely in porphyry-style alteration and mineralization similar to that at the 38 Zone prospect (IL004) about three miles to the northeast. The main-stage mineralization consists of weak, potassium-feldspar alteration with disseminated chalcopyrite, and quartz veins with some chalcopyrite and molybdenite. This mineralization was overprinted by strong sericite-pyrite alteration associated with quartz-pyrite and pyrite veins. Several thin polymetallic veins were intersected in the drill holes. The amount of chalcopyrite decreases markedly with depth, and the density of all of the veins is low along the length of the hole. The extent of this deposit is unknown.
Geologic map unit (-155.487187910207, 59.7772047777202)
Mineral deposit model Porphyry copper-gold-molybdenum deposit (Cox and Singer, 1986; model 20c or 21a).
Mineral deposit model number 20c or 21a
Age of mineralization Probably Late Cretaceous, about 90 Ma, by analogy with the nearby Pebble deposit (IL007).
Alteration of deposit Main stage alteration consists of weak, potassium-feldspar alteration with disseminated chalcopyrite, and quartz veins with some chalcopyrite and molybdenite. The mineralization was overprinted by strong sericite-pyrite alteration associated with quartz-pyrite and pyrite veins.

Production and reserves

Workings or exploration The area has been covered by extensive geochemical and geophysical surveys beginning in about 1986 as part of the exploration of the Pebble block of claims first by Cominco, by it successor Teck-Cominco, and through early 2011 by Northern Dynasty Minerals Ltd. Considerable mapping and sampling at the surface; 1 hole drilled in 2004.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Gaunt, J.D., Rebagliati, C.M., Lang, James, Titley, Eric, Melis, Lawrence, Barratt. Derek, and Hodgson, Stephen, 2010, Technical report on the 2009 program and update on metallurgy, Pebble copper-gold-molybdenum project, Iliamna Lake area, southwestern Alaska, U.S.A: Unpublished Technical Report for Northern Dynasty Minerals Ltd., 195 p. (posted on www.sedar.com, Mar. 18, 2010).
Rebagliati, C.M., and Payne, J.G. 2005, 2004 summary report on the Pebble gold-copper project: Unpublished report for Northern Dynasty Minerals Ltd., 118 p. (posted on www.sedar.com, Apr. 4, 2005).
Reporters D.J. Grybeck (Contractor, USGS)
Last report date 2/28/2011