Wild West

Prospect, Undetermined

Alternative names

Tide Water

Commodities and mineralogy

Main commodities Au
Ore minerals gold; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale B-4
Latitude 55.367
Longitude -131.187
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The Wild West claim adjoins the south side of Gokachin Creek in section 18, T. 75 S., R. 94 E., of the Copper River Meridian. It is roughly parallel to the creek, and extends from the mouth of the creek at Thorne Arm northeastward for about 1450 feet. The location of the map site is roughly at the center of the claim. The site corresponds to loc. 97 in Elliott and others (1978), and to loc. 305 in Maas and others (1995). The location is accurate within 0.1 mile.
See Additional comments.

Geologic setting

Geologic description

The country rocks in this part of Revillagigedo Island are marine, interbedded, andesitic and basaltic metavolcanic rocks and subordinate pelitic metasedimentary rocks that are intruded by stocks, sills, and dikes of Cretaceous feldspar-porphyritic granodiorite (Berg and others, 1988). The strata and some of the granodiorite were regionally metamorphosed to greenschist grade in Late Cretaceous time. These regionally metamorphosed rocks subsequently were locally remetamorphosed to hornblende hornfels near the contacts of Cretaceous granodiorite plutons that were emplaced after the regional metamorphism. The premetamorphic age of the strata is uncertain. Berg and others (1988) assign them a Mesozoic or (late) Paleozoic age. Berg (1982) and Crawford and others (2000) assign them to the Gravina belt, of Late Jurassic or Cretaceous age, or to the Taku terrane, of late Paleozoic to Late Triassic age. The metamorphic and intrusive rocks locally are overlain by basalt and andesite lava flows of Quaternary or Tertiary age.
Brooks (1902, p. 68) describes the Tide Water (subsequently relocated as Wild West) deposit as a well-defined vein, 18 inches wide, that cuts diabase schist and carries a small amount of free gold.
According to Wright and Wright (1908, p. 147), the Wild West prospect consists of several quartz stringers about a foot thick, that strike N60E and dip 70SE. The veins are hosted by banded argillite and sericite schist. At the time of the Wrights' examination, the deposit had been prospected only by surface cuts.
Maas and others (1995, p. 215-218) describe the Wild West deposit as NE-striking quartz fissure veins hosted by hydrothermally altered mafic metavolcanic rocks (see Alteration), and subordinate intercalated metasedimentary rocks. They indicate that the deposit is similar in character and geologic setting to other deposits in the Sea Level mine area (see KC095-098), except that the metavolcanic country rocks at the Wild West prospect contain somewhat more intercalated metasedimentary layers. Workings, all dating to the early 1900s, include a caved adit; 2 shafts, one 23 feet deep and one at least 20 feet deep; and several surface trenches and pits.
Maas and others (1995, p. 215) note that the quartz in the veins in the Sea Level mine area is not recrystallized; the veins thus are probably younger than most or all of the Late Cretaceous regional metamorphism.
Geologic map unit (-131.188693772496, 55.3666600377557)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Maas and others (1995, p. 215) note that the quartz in the veins in the Sea Level mine area is not recrystallized; the veins thus are probably younger than most or all of the Late Cretaceous regional metamorphism.
Alteration of deposit Most of the principal veins in the Sea Level mine area are bordered by a hydrothermally altered zone up to three feet thick, characterized by generally fine-grain, light-gray to bluish-gray, massive, carbonate- and sericite-bearing rock that commonly contains cubic pyrite crystals up to an inch across (Maas and others, 1995, p. 215). Maas and others (1995) interpret this zone as hydrothermally altered mafic metavolcanic rock. Early miners called this altered rock 'blue porphyry,' which they interpreted as crosscutting altered dikes that predate the quartz veins, but are closely associated with some of the orebodies (Brooks, 1902, p. 65; Wright and Wright, 1908, p. 143). Gold content of these pyritic altered zones is high adjacent to the quartz veins and diminishes away from them. Weathered altered rocks have a reddish-brown, oxidized rind up to three inches thick.

Production and reserves

Workings or exploration Workings, all dating to the early 1900s, include a caved adit; 2 shafts, one 23 feet deep and one at least 20 feet deep; and several surface trenches and pits (Maas and others, 1995).
Indication of production Undetermined

Additional comments

The Wild West claim is a relocation of the original Tide Water claim (Wright and Wright, 1908, p. 147).

References

MRDS Number A012350

References

Reporters H.C. Berg, USGS
Last report date 7/4/1999