|Quadrangle map, 1:250,000-scale||CR|
|Quadrangle map, 1:63,360-scale||C-2|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Tacoma and Peacock claims are about 0.5 mile southeast of the Rich Hill Mine (CR063) and about 0.3 mile north of triangulation station Cole. The claims are about about 0.5 mile southeast of the center of section 21, T. 73 S., R. 86 E.|
The Tacoma claim contains small, irregular, contact-metamorphic deposits that consist of chalcopyrite, magnetite, and minor molybdenite, in garnet-epidote rock (Warner and others, 1961). The deposit is exposed on the beach and in a 60-foot adit. The Peacock claim extends north from the Tacoma claim. At an elevation of about 120 feet, a 45-foot-long tunnel cuts a belt of garnet-epidote rock that contains magnetite and minor chalcopyrite. At an elevation of about 325 feet, an adit 30 feet long exposes similar garnet-epidote rock adjacent to a diabase dike. Wright and Wright (1906) reported that considerable ore had been mined from one or both of the claims and was awaiting shipment.
The Peacock and Tacoma claims contain several small prospects similar to many of the other copper-iron deposits on the Kasaan Peninsula having similar geology and origin (Warner and others, 1961; Eberlein and others, 1983; Brew, 1996). The rocks on the peninsula consist mainly of andesite ('greenstone' in much of the older literature) interbedded with about 25 percent sedimentary rocks comprising approximately equal amounts of limestone or marble, calcareous mudstone and sandstone, and graywacke and conglomerate. These units are part of the Luck Creek Breccia of Silurian and Devonian age, but many of the sedimentary units are similar to and probably grade into rocks of the Silurian and Ordovician, Descon Formation. The bedded rocks are intruded by a profusion of Silurian or Ordovician dikes, sills, and irregular masses of porphyritic gabbro, basalt, andesite, diorite, dacite, and granodiorite. Near some of the deposits, these intrusions may make up 20 percent or more of the outcrop and usually are associated with the development of tactite and alteration of the greenstone. The area subsequently was intruded by several large Silurian or Ordovician plutons; they are mainly granodiorite but locally are diorite and gabbro.
The ore deposits are typically small and of irregular shape; often the ore bodies form lenses or mantos. Some of the deposits conform to the layering in the greenstone and sedimentary rocks. The principal ore minerals are chalcopyrite, pyrite, and magnetite; hematite is often present and a little molybdenite occurs in some deposits. Most of the deposits are associated with tactite or skarn with varying amounts of actinolite, calcite, chlorite, garnet, diopside, epidote, and hornblende. There was significant by-product silver and gold in the ore that was mined in the past, and the gold values in some deposits are high enough to have encouraged exploration in recent years. Marble is more common in the deposits in the western part of the peninsula, where the gold values are generally higher as well (Wright and Wright, 1908; Wright, 1915; Warner and others, 1961; Myers, 1985; Bond, 1993; Maas and others, 1995).
Early interpretations of the ore deposits on the Kasaan Peninsula emphasize their contact metamorphic origin and their probable Mesozoic age (for example, Warner and others, 1961). However, recent radiometric dating and mapping indicate that the deposits formed in a Silurian or Ordovician, arc-related environment characterized by deposition of andesite and submarine sedimentary rocks that were intruded by swarms of dikes of varying composition, mineralized, and then intruded by large granodiorite plutons (Hedderly-Smith, 1999 [Inventory]).The copper deposits of the Kasaan Peninsula were known to the Russians and the first claim was staked in 1867. Most of the production and development occurred from about 1900 to 1918, especially from 1905 to 1907, when copper prices soared and a smelter was built at Hadley on the north side of the Kasaan Peninsula. After World War I, copper supply exceeded demand, prices fell, and there has been no further copper production since 1918 (Wright, 1915; Warner and others, 1961; Roppel, 1991; Maas and others, 1995). However, because of the intense and widespread mineralization on the peninsula, the area has repeatedly been re-examined for copper, iron, and gold, notably during WW II (Warner and others, 1961) and in the last several decades.
|Geologic map unit||(-132.338282575243, 55.5208678561026)|
|Mineral deposit model||Cu-Fe skarn (Cox and Singer, 1986; model 18d).|
|Mineral deposit model number||18d|
|Age of mineralization||The deposit formed in a Silurian or Ordovician, submarine arc-related environment characterized by the deposition of volcanic and sedimentary rocks, the intrusion of swarms of dikes of diverse composition, and the emplacement of several large plutons.|
|Alteration of deposit||Pervasive development of tactite.|
|Workings or exploration||Explored by several pits and two adits.|
|Indication of production||None|
|Production notes||Wright and Wright (1906) reported that considerable ore had been mined from one or both of the claims and was awaiting shipment. However, there is no indication that the ore was actually shipped.|
Additional commentsThese old claims are on or surrounded by land whose surface rights are held by the Sealaska Corporation.
|MRDS Number||A010; A010096|
Bond, R.W., 1993; The mineralogy and geochemistry of the Kasaan Peninsula, iron-copper-silver-gold skarns, Prince of Wales Island, southeastern Alaska: Salt Lake City, University of Utah, M.Sc. thesis, 130 p.
Brew, D.A., 1996, Geologic map of the Craig, Dixon Entrance, and parts of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2319, 53 p., 1 sheet, scale 1:250,000.
Eberlein, G.D., Churkin, Michael, Jr., Carter, Claire, Berg, H.C., and Ovenshine, A. T., 1983, Geology of the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 83-91, 52 p.
Hedderly-Smith, D.A., 1999, Inventory of metallic mineral prospects, showings and anomalies on Sealaska lands, 1988 through 1998: Sealaska Corporation, Juneau, Alaska, 217 p. (internal report held by Sealaska Corporation, Juneau, Alaska).
Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p.
Myers, G.L., 1985, Geology and geochemistry of the iron-copper-gold skarns of Kasaan Peninsula, Alaska: Fairbanks, University of Alaska, M.Sc. thesis, 165 p.
Roppel, Patricia, 1991, Fortunes from the earth: Manhattan, Kansas, Sunflower University Press, 139 p.
Warner, L.A., Goddard, E.N., and others, 1961, Iron and copper deposits of Kasaan Peninsula, Prince of Wales Island, southeastern Alaska: U.S. Geological Survey Bulletin 1090, 136 p.
Wright, C.W., 1915, Geology and ore deposits of Copper Mountain and Kasaan Peninsula, Alaska: U.S. Geological Survey Professional Paper 87, 110 p.
Wright, C.W., and Paige, Sidney, 1908, Copper deposits on Kasaan Peninsula, Prince of Wales Island, in Brooks, A.H., and others, Mineral resources of Alaska: report on progress of investigations in 1907: U.S. Geological Survey Bulletin 345, p. 98-115.
Wright, F.E., and Wright, C.W., 1906, Lode mining in southeastern Alaska, in Brooks, A.H., 1906, Report on Progress of Investigations of Mineral Resources of Alaska in 1905: U.S. Geological Survey Bulletin 284, p. 30-54.
|Reporters||D.J. Grybeck (Applied Geology)|
|Last report date||5/1/2004|