Unnamed (east of Chistochina River) (ARDF #MH291) Ag, Cu

Unnamed (east of Chistochina River)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities	Ag; Cu
Ore minerals	azurite; chalcopyrite; malachite; pyrite
Gangue minerals	actinolite; albite; chlorite; epidote; potassium feldspar; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale	MH
Quadrangle map, 1:63,360-scale	A-2
Latitude	63.1239
Longitude	-144.9047
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is about 1.5 miles east-southeast of the junction of the Chistochina River and the West Fork Chistochina Rivers. The occurrence is about one-third mile east of the center of section 5, T. 21 S., R. 15 E., Fairbanks Meridian. It corresponds to locality 138 in table 2 of Nokleberg and others (1991), and the location is probably accurate to 0.2 mile.

Geologic setting

Geologic description This occurrence is in dacite porphyry of Early Permian age. The dacite intrudes the lower part of the Slana Spur Formation of Pennsylvanian to Early Permian age; the Slana Spur Formation is mainly composed of dacite agglomerate. Locally, the dacite porphyry is intensely altered to a rock composed of actinolite, albite, chlorite, epidote, potassium feldspar, and sericite. This occurrence is a dacite porphyry that contains disseminated pyrite and chalcopyrite and is locally stained with azurite and malachite. A grab sample assayed 1.14 percent copper and 50 parts per million silver (Nokleberg and others, 1991). The deposit is probably a porphyry copper related to the Early Permian dacite porphyry.
Geologic map unit	(-144.906920955354, 63.1234980856209)
Mineral deposit model	Probably Porphyry Cu (Cox and Singer, 1986; model 20c).
Mineral deposit model number	20c
Age of mineralization	Probably Early Permian.
Alteration of deposit	Locally intense alteration of dacite. Alteration minerals include actinolite, albite, chlorite, epidote, potassium feldspar, and sericite.

Production and reserves

Workings or exploration	Limited surface sampling; no workings reported from the site.
Indication of production	None
Additional comments More prospecting appears to be warranted.

References

References Nokleberg, W.J., Lange, I.M., Roback, R.C., Yeend, Warren, and Silva, S.R., 1991, Map showing locations of metalliferous lode and placer mineral occurrences, mineral deposits, prospects, and mines, Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1996-C, 42 p., 1 sheet, scale 1:250,000.
Reporters	W.T. Ellis (Alaska Earth Sciences) and C.C Hawley (Hawley Resource Group)
Last report date	7/9/2003