Unnamed (mouth of Johns Hopkins Inlet) (ARDF #MF049) Zn

Unnamed (mouth of Johns Hopkins Inlet)

Occurrence, Inactive

Commodities and mineralogy

Main commodities	Zn
Other commodities	Ag; Au; Cu; Pb
Ore minerals	chalcopyrite; galena; pyrite; pyrrhotite; sphalerite
Gangue minerals	calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale	MF
Quadrangle map, 1:63,360-scale	D-3
Latitude	58.921
Longitude	-136.93
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	The occurrence is about 0.3 mile north of the point that separates Tarr and Johns Hopkins Inlets. It is close to the shore line, and is known within a few hundred feet. The location is number 45 of Kimball and others (1978).

Geologic setting

Geologic description The area is mainly underlain by heterogeneous granitic rocks of Cretaceous age (Brew and others, 1978). The granitic rocks are cut by a quartz-calcite vein as much as 3.5 feet thick which contains lenses of iron sulfide-rich massive sulfide. Sphalerite and chalcopyrite are also present in the sulfide lenses. The quartz-calcite vein can be traced for about 100 feet to overburden cover. A sample across the widest part of the vein contained 4,300 ppm zinc and lesser quantities of other base and precious metals. The vein occurrence probably has one of two affinities. It may be related to the Orange Point (MF038) base metal-type mineralization, or it could represent the northwest limit of the Reid Inlet gold area, whose major deposits are the LeRoy (MF022), Rainbow (MF027), Rambler (MF028) and Highland Chief (MF030). Although the most productive veins of the Reid Inlet area were gold-rich, sphalerite occurs widely and in some veins is predominant.
Geologic map unit	(-136.931878779832, 58.9205956612728)
Mineral deposit model	Polymetallic quartz-calcite vein -- similar to polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number	22c
Age of mineralization	Cretaceous or younger.

Production and reserves

Workings or exploration	Surface exposure, no workings. A chip sample of the full width of the vein (3.5 feet) contained 4,300 ppm zinc, 770 ppm copper, 250 ppm lead, 15 ppm silver, and 0.03 ppm gold (Kimball and others, 1978, table C39, p. C191).
Indication of production	None
Additional comments Worth additional prospecting, as possibly related to Orange Point or Reid Inlet mineralization. Prospect is in Glacier Bay National Park and Preserve.

References

MRDS Number	A013148
References Brew, D.A., Johnson, B.R., Grybeck, D., Griscom, A., Barnes, D.F., Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources of the Glacier Bay National Monument Wilderness Study Area, Alaska: U.S. Geological Survey Open-File Report 78-494, 670 p., 7 sheets. Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources, in Brew, D. A., and others, Mineral resources of the Glacier Bay National Monument wilderness study area, Alaska: U.S. Geological Survey Open-File Report 78-494, p. C1-C375.
Reporters	C.C. Hawley (Hawley Resource Group)
Last report date	4/9/1999