|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||There are several deposits at this site that are unnamed or described under different names. Several of descriptions are probably of the same deposit but some of the locations are not precise and it is unclear how many different deposits are present. See the 'Geologic description' field for the locations of the individual deposits. The site is somewhat arbitrarily plotted about 0.4 mile east-southeast of the center of section 9, T. 72 S., R. 85 E., about 0.5 mile southeast of Tolstoi Mountain. Several of the deposits are probably quite close to this location and all are probably with a mile. The geology and workings in the area are shown on plates 16 and 17 of Warner and others (1961).|
Warner and others (1961) describe a quartz vein with magnetite and chalcopyrite about 2,500 feet S25E from Tolstoi Mountain. The vein is exposed in a stream along a major fault zone. The vein consists of vuggy quartz with chalcopyrite in the vugs. The vein has been explored by an adit that follows the vein for about 20 feet until it feathers out into small stringers. The rocks in the area consist largely of conglomerate, calcareous siltstone and sandstone, and greenstone, cut by many diorite dikes. This is probably near the Wallace Group that Wright and Wright (1908) describe as containing small, scattered masses of garnet-epidote rock with chalcopyrite and magnetite and which has been explored by at least one adit. Hedderly-Smith (1999 [Inventory]) describes adits, some trenches, and a dump between about 1,150 and 1,220 feet elevation in this vicinity. Several samples of float and dump rock contained up to 8.9 percent copper, 44.6 percent iron, 40.6 parts per million (ppm) silver, and 3.8 ppm gold.
Roehm (1938 [PE 119-14]) describes the Mucker's Dream Group, a prospect about two miles north of Windfall Harbor; it is probably in this area. The workings consist of trenches at elevations of about 740 and 920 feet; a 55-foot adit with a 15-foot crosscut at an elevation of about 1,200 feet; and a long trench, an adit, and a shaft at an elevation of about 1,240 feet. The original discovery was in 1914. In 1916, 10 tons of ore returned $85 in gold per ton; a 3-ton shipment in 1922 also returned $85 in gold per ton. The property was still being worked in 1938. The rocks in the area consist mainly of greenstone and the deposits are along a major N30-35W fault that is probably the same fault that Warner and others (1961, plate 16) show west of Tolstoi Mountain. In one adit, a 12-inch quartz vein with chalcopyrite, pyrite, hematite, and magnetite contained 0.02 ounce of gold per ton. In another adit, high-grade copper-gold ore in a quartz vein cuts garnet-epidote rock. A sample of this vein contained 0.68 ounce of gold per ton and 1.40 ounces of silver per ton. The higher-grade ore in these quartz veins reportedly was similar to the ore in the contact metamorphic copper deposits of the Kasaan Peninsula.
Wright and Wright (1908) describe the Tolstoi Group of claims, which are south of the Wallace Group, just below the summit of Tolstoi Mountain. The ore bodies are low-grade magnetite-chalcopyrite masses similar to those at the Iron Cap prospect (CR066).
These prospects are probably related in origin and geologic setting to the numerous copper-iron deposits on the Kasaan Peninsula, although they are among the few where gold-quartz veins are specifically mentioned. 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||(-132.379173949393, 55.6396635812797)|
|Mineral deposit model||Gold-quartz vein and Cu-Fe skarn (Cox and Singer, 1986; models 18d and 36a).|
|Mineral deposit model number||18d, 36a|
|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||Extensive development of skarn.|
|Workings or exploration||Several to many adits and trenches depending on the number of different deposits that are included in this site.|
|Indication of production||None|
Anzman, J.R., 1995, Airborne geophysical survey, Kasaan Peninsula, Alaska, 12 p. (Unpublished report held by Sealaska Corporation, Juneau, Alaska).
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.
Cobb, E. H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Craig quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-869, 262 p.
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., 1993, Report of the 1992 field season-Sealaska minerals reconnaissance project: Sealaska Corporation, 60 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1997, Report on the 1995 and 1996 work on the Kasaan Peninsula-Sealaska minerals project: Sealaska Corporation, 87 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1998, Report of the 1995-1997 work on the Kasaan Peninsula-Sealaska minerals project: Sealaska Corporation, 130 p. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
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.
Roehm, J.C., 1938, Preliminary report of Mucker's Dream group, Windfall Bay, Prince of Wales Island: Alaska Territorial Department of Mines Property Examination 119-14, 3 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.
|Reporters||D.J. Grybeck (Applied Geology)|
|Last report date||5/1/2004|