Pelaska

Prospects, Probably inactive

Alternative names

Hilma
Sunrise
Venus
Pennsylvania

Commodities and mineralogy

Main commodities Cu
Ore minerals chalcopyrite; magnetite; pyrite
Gangue minerals calcite; epidote; garnet

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale C-1
Latitude 55.53505
Longitude -132.30321
Nearby scientific data Find additional scientific data near this location
Location and accuracy Prior to WW I, many claims were staked west of the head of Lyman Anchorage in what was then called 'Hole in the Wall' (Wright, 1915). There is little specific information about the location of most of these claims and prospects and this site is somewhat arbitrarily plotted about 0.3 mile west of the site of Hadley, in the SW1/4 section 14, T. 73 S., R. 86 E. This site is near the workings on the Hilma claim at an elevation of about 310 feet. The other prospects may be 0.5 mile or more away.

Geologic setting

Geologic description

Prior to WW I, many claims were staked near the contact between contact-metamorphosed limestone and diorite west of 'Hole in the Wall,' a constricted basin at the the head of Lyman Anchorage (Wright and Wright, 1908; and Wright 1915) At the Hilma claim, 1/2 mile northwest of the head of the bay at an elevation of 310 feet, a 25-foot tunnel at a limestone-diorite contact exposes small masses of garnet-epidote-calcite tactite with chalcopyrite. The Eureka claim, near tidewater at the head of the bay, has similar mineralization. At an elevation of about 1,050 feet on the Sunrise claims, a 25-foot-wide contact zone contains considerable chalcopyrite and magnetite; and at an elevation of about 950 feet, an open cut exposed coarsely crystalline marble and small amounts of tactite containing some chalcopyrite. On the Pennsylvania claims, an open cut at an elevation of about 850 feet follows a felsite dike and exposes a 2- to 3-foot-wide vein with pyrite and minor chalcopyrite. At the Pelaska claims, which extend west from the head of the bay, a 100-foot tunnel follows a belt of altered limestone cut by a diabase dike. Garnet-epidote rock with minor chalcopyrite occurs at the contact.
The small deposits at this site are similar in geology and origin to many copper-iron deposits on the Kasaan Peninsula (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 (-132.304892504236, 55.5346878552645)
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 in greenstone and marble.

Production and reserves

Workings or exploration Numerous claims were staked in the area prior to 1918, and two short adits and several trenches explored a number of occurrences of copper mineralization near the contact of limestone with diorite.
Indication of production None
Reserve estimates None.
Production notes None, although Bufvers (1967) noted that 50 tons of material was mined at the Pelaska prospect and left on the dump.

References

MRDS Number A010021

References

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.
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).
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.
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004