Prospect, Undetermined

Commodities and mineralogy

Main commodities Au; Pb; Zn
Ore minerals galena; gold; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale B-4
Latitude 55.389
Longitude -131.183
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Tyee prospect is at an elevation of about 250 feet, on the north bank of the creek just below the outlet of Granite Lake. The site is in section 6, T. 77 S., R. 94 E., of the Copper River Meridian. It corresponds to loc. 85 in Elliott and others (1978), and to loc. 297 in Maas and others (1995). The location is accurate within 0.1 mile.

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.
The Tyee deposit consists of a four-foot-wide quartz fissure vein in granodiorite (Wright and Wright, 1908, p. 148). The vein strikes east and dips 78S, and contains small amounts of pyrite, sphalerite, and galena, accompanied by low values in gold. According to Maas and others (1995, p. 215), the quartz in the veins is not recrystallized, so the veins probably are younger than most or all of the Late Cretaceous regional metamorphism.
Geologic map unit (-131.184694453723, 55.3886596531897)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Late Cretaceous or younger.

Production and reserves

Indication of production None