Lakeside

Mine, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Co; Ni
Ore minerals chalcopyrite

Geographic location

Quadrangle map, 1:250,000-scale DE
Quadrangle map, 1:63,360-scale D-3
Latitude 54.9952
Longitude -132.7565
Nearby scientific data Find additional scientific data near this location
Location and accuracy This is an old mine on a narrow neck of land on the west side of Sukkwan Island. It is about 0.4 mile north of the southern tip of the island in the NE1/4 section 28, T. 79 S., R. 84 E., of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Lakeside Mine was first described by Chapin in 1918 and little work has been done on it since. The rocks in the vicinity consist of locally pegmatitic, Ordovician gabbro and hornblendite and Silurian or Ordovician basaltic volcanic rocks (Gehrels, 1991). The gabbro has been dated at 440 Ma and 449 Ma (Eberlein and others, 1983).
According to Chapin (1918), two shear zones contain chalcopyrite. One shear zone is about 5 feet wide, strikes N20W and dips NE; the other is about two feet wide, vertical, and strikes N20W. In 1916, the workings consisted of a 41-foot shaft and a 41-foot crosscut that interested both shear zones. Roehm (1941) indicated that the deposit had been developed by a 100-foot shaft with 50-foot drifts at the 50-foot level and at the bottom of the shaft. He also indicated that there had been copper production in 1917 and 1918.
Maas and others (1991, p. 47) indicate that the chalcopyrite occurs in irregular pods, disseminations, and seams in two fault zones that strike N 35 W; the faults are near a gabbro-basalt contact. Their best samples contained 1.57 percent copper, 0.28 percent nickel, and 892 parts per million cobalt; all of the samples contained less than 5 parts per billion platinum-group metals. (Wilcox (1937 [PE 121-2]) mentioned the potential for Pt-group metals at this site.)
Geologic map unit (-132.758158041775, 54.9948533694658)
Mineral deposit model The deposit may be magmatic (syngenetic) and contemporaneous with the Ordovician gabbro hostrock, or it may be epigenetic and younger.
Age of mineralization Silurian or Ordovician or younger.

Production and reserves

Workings or exploration Roehm (1941) indicated that the deposit had been developed by a 100-foot shaft with 50-foot drifts at the 50-foot level and the bottom of the shaft.
Indication of production Yes
Production notes Roehm (1941) states that there was copper production in 1917 and 1918.

References

MRDS Number A010259

References

Reporters D.J. Grybeck (Applied Geology)
Last report date 9/1/2003