Riverside; Riverview; Lindeborg Mine, Hyder Mining District, Prince of Wales-Hyder Census Area, Alaska, USAi

Regional Level Types
Riverside; Riverview; Lindeborg Mine	Mine
Hyder Mining District	Mining District
Prince of Wales-Hyder Census Area	Census Area
Alaska	State
USA	Country

Deposit probably originally staked about 1915-1920. Some descriptions of the Riverside mine refer to it as the Riverview or Lindeborg property (Cobb, 1978, p. 66).
Location: The Riverside mine is near the west boundary of Section 2 at an elevation of about 500 feet (main adit), and just east of the road running along the Salmon River (Elliott and Koch, 1981, p. 20, loc. 80). The location is accurate within about 100 feet. Also see Additional Comments field, below.
Geology: The country rocks in the area of the Riverside mine are the Triassic Texas Creek Granodiorite, which underlies and locally intrudes pelitic metasedimentary and subordinate andesitic (greenstone) metavolcanic strata of the Jurassic or older Mesozoic Hazelton Group; the Eocene Hyder Quartz Monzonite, which intrudes the Texas Creek and Hazelton rocks; and still-younger Tertiary lamprophyre dikes, which cut all the other rocks (Smith, 1973, 1977; Koch, 1996). The deposit (Chapin, 1916, p. 97; Westgate, 1922, p. 139; Buddington, 1925, p. 74-75, 79-82; 1929, p. 43, 77-81; Thorne and others, 1948, p. 4-5; Byers and Sainsbury, 1956, p. 125-136; Noel, 1966, p. 53-55; Cobb, 1978, p. 66-69) consists of two or three main quartz fissure veins up to 7 feet thick in Texas Creek Granodiorite, and the Lindeborg deposit, which is either a mineralized shear zone in a Hazelton schist inclusion in the granodiorite (according to most workers), or a mineralized zone of mylonitic gneiss and ultramylonite derived from the granodiorite (according to Smith, 1977, p. 17-18). The Lindeborg deposit contains considerable scheelite; the quartz veins carry only small amounts. Other than scheelite, the principal ore minerals are galena, pyrite, tetrahedrite, pyrrhotite, chalcopyrite, sphalerite, and native gold. The principal gangue mineral is quartz, accompanied by small amounts of calcite, ankerite, and barite. In the Texas Creek Granodiorite, the scheelite-bearing lodes (Byers and Sainsbury, 1956, p. 125-136) are mineralized shoots in quartz fissure veins. In the Lindeborg shear zone, they are in part quartz fissure veins and in part replacement deposits. Scheelite in the Lindeborg zone appears to have preferentially replaced calcareous laminae in the schist hostrock. The Lindeborg lode is about 3 feet thick and has been traced in outcrop for 2000 feet and through a vertical interval of more than 700 feet. Lead-isotope studies of galena from the Riverside mine (Maas and others, 1995, p. 254) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Workings: The Riverside mine operated discontinuously from 1925-1951. It was developed by more than 6000 feet of underground workings and explored by about 4600 feet of diamond drill holes, mainly during World War II.
Age: Lead-isotope studies of galena from the Riverside mine (Maas and others, 1995, p. 254) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Production: From 1925-1951, the Riverside mine yielded about 30,000 tons of ore. Almost all of the ore was from the Lindeborg lode, which produced about 3,000 oz Au, 100,000 oz Ag, 100,000 lb Cu, 250,000 lb Pb, 20,000 lb Zn, and 70,000 lb WO3.

Commodities (Major) - Ag, Au, Cu, Pb, W, Zn; (Minor) - Barite
Development Status: Yes; small
Deposit Model: Polymetallic veins

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Link to USGS - Alaska:	BC080

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References