|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 Poor Man Mine is shown on the USGS 1:63,360-scale topographic map; it is about 0.6 mile northwest of the center of section 12, T. 73 S., R. 85 E. The geology and workings are the Poorman Mine are shown on plates 12 to 15 of Warner and others (1961).|
The Poorman deposit is in greenstone containing layers of quartzite and graywacke and lenses of marble, all intruded by a multitude of dikes of intermediate to basic composition. The rocks are cut by a series of north-trending, en echelon faults. The deposit is essentially a magnetite lens about 100 feet wide and 1,500 feet long at the surface; the lens lies along one of the faults and dips 60-80W. The magnetite body contains less than 10 percent pyrite and chalcopyrite; the chalcopyrite usually occurs in a network of quartz-calcite veinlets in the magnetite. About 10 percent of the deposit consists of fragments of altered greenstone and dike material. The mineralization appears to preferentially replace shattered greenstone. The magnetite lens is bordered by several feet of lower-grade material containing disseminated chalcopyrite, pyrite, and magnetite.
The deposit was originally developed as a copper prospect, but since WWII has mainly been considered to be a high-grade iron deposit with copper values. It has been explored by 3 short adits, 4 shafts, and numerous pits and trenches. During World War II, the U.S. Bureau of Mines diamond drilled 13 holes and delineated the full extent of the body by a dip-needle survey. In recent years, the deposit has been drilled as part of a patent application process, and the drilling has revealed additional shallow magnetite bodies.
Holt and Sanford (1946) estimate that the deposit contains about 900,000 tons of measured and indicated ore and 450,000 tons of inferred ore. The body averages 52.4 percent iron, 0.25 percent copper, 0.032 ounce of gold per ton, and 0.071 ounce of silver per ton.
The Morning Star, Blackbird, and Copper King are old prospects nearby (Brooks, 1902; Chapin, 1916) that probably became part of the Poorman property.
The Poorman prospect is one of many 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||(-132.437568925054, 55.5578736294829)|
|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||Development of calc-silicate skarn.|
|Workings or exploration||The property has been explored by 3 short adits, 4 shafts, and numerous pits and trenches. During World War II, the U.S. Bureau of Mines diamond drilled 13 holes and delineated the full extent of the ore body by a dip-needle survey. In 1989 and 1990, the claims were being drilled as part of an application for patent, and the drilling revealed additional magnetite bodies. In 1998, three claims were patented.|
|Indication of production||None|
|Reserve estimates||Holt and Sanford (1946) estimate that the deposit contains about 900,000 tons of measured and indicated ore and 450,000 tons of inferred ore. The body averages 52.4 percent iron, 0.25 percent copper, 0.032 ounce of gold per ton, and 0.071 ounce of silver per ton. Drilling in 1989 and 1990 as part of an application for patent discovered several additional magnetite bodies.|
Additional commentsThe surrounding area consists of land that has been conveyed to the Sealaska Corporation, who hold the surface and subsurface rights, or the land is under application for transfer to them.
|MRDS Number||A010007; A010023; A010134|
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.
Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p.
Brooks, A.H., 1921, The future of Alaska mining, in Martin, G.C., and others, Mineral resources of Alaska, 1917: U.S. Geological Survey Bulletin 714-A, p. 5-57.
Buddington, A.F., and Chapin, Theodore, 1929, Geology and mineral deposits of southeastern Alaska: U.S. Geological Survey Bulletin 800, 398 p.
Bufvers, John, 1967, History of mines and prospects, Ketchikan district, prior to 1952: Alaska Division of Mines and Minerals Special Report 1, 32 p.
Chapin, Theodore, 1916, Mining developments in southeastern Alaska: U.S. Geological Survey Bulletin 642-B, p. 73-104.
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., 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).
Holt, S.P., and Sanford, R.S., 1946, Exploration of Poor Man iron deposit, Kasaan Peninsula, Prince of Wales Island, southeastern Alaska: U.S. Bureau of Mines Report of Investigation 3956, 8 p.
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.
Maas, K.M., Still, J.C., and Bittenbender, P.E., 1992, Mineral investigations in the Ketchikan mining district, Alaska, 1991 - Prince of Wales Island and Vicinity: U.S. Bureau of Mines Open-File Report 81-92, 69 p., 1 sheet, scale 1:20.
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.
Smith, S.S., 1917, The mining industry in the Territory of Alaska during the calendar year 1916: U.S. Bureau of Mines Bulletin 153, 89 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.
Wells, R.R., Erspamer, E.G., and Sterling, F.T., 1957, Beneficiation of iron-copper ores from Kasaan Peninsula, Prince of Wales Island, Alaska: U.S. Bureau of Mines Report of Investigation 5312, 15 p.
Wright, C.W., 1907, Lode mining in southeastern Alaska, in Brooks, A.H., and others, Report on progress of investigations of mineral resources of Alaska in 1906: U.S. Geological Survey Bulletin 314, p. 47-72.
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|