Unnamed (east of Waterfall Lake) (ARDF #SI129) Cu

Unnamed (east of Waterfall Lake)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities	Cu
Ore minerals	malachite
Gangue minerals	epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale	SI
Quadrangle map, 1:63,360-scale	C-6
Latitude	57.5325
Longitude	-135.8158
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is at an elevation of about 1,000 feet, about 1.8 miles east of the outlet of Waterfall Lake. The occurrence is 0.2 mile southeast of the center of sec. 17, T. 50 S., R. 60 E. It is location 43 of Cobb (1972, 1978). The location probably is accurate within 0.2 mile.

Geologic setting

Geologic description Johnson and Karl (1985) map the rocks in the area of this occurrence as Triassic(?) greenstone that is intruded by a northwest-striking, linear sill(s) of Cretaceous(?) diorite. The rocks are cut by steeply-dipping, mainly northwest-striking faults; these include the regional-scale Border Ranges Fault whose trace is just southwest of the occurrence. The fault apparently is intruded by the sill(s). Cobb (1972, 1978), citing Loney and others (1963), describes the occurrence as secondary copper minerals in quartz and epidote amygdules in greenstone. Triassic(?) greenstone elsewhere on northwest Chichagof Island generally contains primary copper minerals that are about the same age as the greenstone host rock (see, for example, SI035 and SI036).
Geologic map unit	(-135.817604624517, 57.5321424240164)
Mineral deposit model	Basaltic copper (Cox and Singer, 1986; model 23).
Mineral deposit model number	23
Age of mineralization	Triassic(?) greenstone elsewhere on northwest Chichagof Island generally contains primary copper minerals that are about the same age as the greenstone host rock.

Production and reserves

Indication of production	None
Additional comments The occurrence is in West Chichagof-Yakobi Wilderness.

References

MRDS Number	A013288
References Cobb, E.H., 1972, Metallic mineral resources map of the Sitka quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-467, scale 1:250,000. Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Sitka quadrangle: U.S. Geological Survey Open-File Report 78-450, 124 p. Loney, R.A., Berg, H.C., Pomeroy, J.S., and Brew, D.A., 1963, Reconnaissance geologic map of Chichagof Island and northwestern Baranof Island, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-388, 1 sheet, scale 1:250,000.
Reporters	H.C. Berg (U.S. Geological Survey)
Last report date	10/16/2004