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Pika Canyon

Prospect, Inactive

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Commodities and mineralogy

Main commodities Ag; Au
Other commodities Cu; Pb
Ore minerals chalcopyrite; galena; malachite; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale TC
Quadrangle map, 1:63,360-scale D-1
Latitude 63.8267
Longitude -141.4061
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Pika Canyon prospect is located in a saddle that is at the headwaters of a tributary of Dude Creek to the west and a tributary of Liberty Creek to the east. The prospect location covers about 1/2 square mile and has been updated from previous reporting based on recent work where mineralization in rocks and soils has been found in the southeast corner of section 30, T. 24 N., R. 21 E. of the Copper River Meridian.

Geologic setting

Geologic description

The dominant lithology at the Pika Canyon prospect is augen gneiss having a possible igneous protolith (Mertie, 1931; Foster, 1970). This protolith has a possible emplacement age (inferred from dating other exposures in the region) of Devonian to Mississippian (360 Ma), with resets in the Late Jurassic (190 Ma) and Early to Mid-Cretaceous (135-107 Ma) time (Dusel-Bacon and Aleinikoff, 1985). A series of plugs and dikes which range in composition from diorite to monzodiorite intrude the augen gneiss. Based on cross-cutting relationships and minimal alteration within these units, these intrusions are interpreted to be syn- to post-mineralization in age. The mapped intrusions directly correspond with magnetic highs in the regional 1:50,000 scale magnetic survey conducted by Full Metal Minerals-BHP Billington (King and Tedeschi, 2012). Based on similarities to nearby dated plutons, the Pika Canyon intrusions are likely members of the Prospector Mountain Suite formed during the development of a volcanic arc during the Late Cretaceous (Selby and Creaser, 2001).
The alteration in the greater Pika Canyon area is patchy and somewhat irregular, but generally occurs in somewhat concentric zones of potassic, phyllic, and propylitic alteration (Gill, 1977). Significant brecciation and extensive alteration occurs along the contact of the diorite dike with the augen gneiss located in the saddle of Pika Canyon, indicating it was a conduit for hydrothermal fluids. Mineralization at Pika Canyon consists of gold-silver rich quartz vein stockwork in augen gneiss at and near the contact with the diorite dike. Alteration of the augen gneiss is zoned based on distance from the diorite contact. Distally, alteration is weak consisting of biotite destruction replaced by fine grained sericite and iron oxides. Weak alteration grades into strong to moderate sericite and silicification towards the contact. Silicification is most commonly manifested as thin sheeted veins and stockwork exploiting foliation, but occasionally crosscuts primary fabric, including augens. These foliation parallel veins range in thickness from 1 to 10 millimeters and occasionally contain jarosite and iron oxides, indicative of the former presence of sulfide minerals. Typically these veins are clear to bluish in color and are very fine grained (King and Tedeschi, 2012).
Geologic map unit (-141.412254894254, 63.8296810505183)
Mineral deposit model Creede epithermal veins? (low-sulfidation epithermal) (Cox and Singer, 1986; model 25b).
Mineral deposit model number 25b?
Age of mineralization Mineralization was likely synchronous with faulting and magmatism during Late Cretaceous (70 to 68 Ma), indicated from dated hydrothermal mica (Allan and others, 2015).
Alteration of deposit
The alteration in the greater Pika Canyon area is patchy and somewhat irregular, but generally occurs in somewhat concentric zones of potassic, phyllic, and propylitic alteration (Gill, 1977).
In the saddle of Pika Canyon alteration of the augen gneiss is zoned based on distance from the diorite contact. Distally, alteration is weak consisting of biotite destruction replaced by fine grained sericite and iron oxides. Weak alteration grades into strong to moderate sericite and silicification towards the contact. Silicification is most commonly manifested as thin sheeted veins and stockwork exploiting foliation, but occasionally crosscuts primary fabric, including augens (King and Tedeschi, 2012).

Production and reserves

Workings or exploration
During 1974 to 1976, soil, rock chip, and stream-sediment sampling were conducted on the prospect, as well as a ground magnetic survey on a 200- by 500-foot grid (Gill, 1977, p. 2).
In 2008 Full Metal Minerals (FMM) and BHP Billington completed a regional 1:50,000 scale magnetic survey that covered the Pika Canyon area. Magnetic highs at Pika Canyon correspond with mapped monzodiorite and diorite intrusions (King and Tedeschi, 2012).
FMM completed ridge and spur soil sampling and geologic mapping over the Pika Canyon prospect in the early part of the summer in 2011. Positive gold and silver results in these soil samples led to a soil grid put in place the same year over the Pika Canyon area with 190 more soil samples collected. With limited outcrop available, trenching over an area with altered float led to the discovery of the diorite dike with mineralized and brecciated contact zones with the augen gneiss (King and Tedeschi, 2012).
Indication of production None

References

MRDS Number A012532

References

Cox, D.P., and Singer, D.A., eds., 1986, Mineral deposit models: U.S. Geological Survey Bulletin 1693, 379 p.
Mertie, J.B., Jr., 1931, A geologic reconnaissance of the Dennison Fork district, Alaska: U.S. Geological Survey Bulletin 827, 44 p.
Reporters C.E. Cameron (ADGGS), N.V. King (Alaska Earth Sciences)
Last report date 2/25/2016