Olympic Peninsula deposits

Region West, Northwest
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Arcuate distribution of Eocene basaltic rocks and interlayered red siliceous limestones and limey argillites.
Identified resources Historical production of manganese.
Production Crescent Mine: 50,000 tons of ore (largely hausmannite).
Status Past mining.
Estimated resources For 17 Olympic Peninsula deposits, the median tonnage is 340 tons, and the median Mn grade is 35% (Mosier and Page, 1988).
Geologic maps Gerstel and Lingley (2003), scale 1:100,000; Tabor and Cady (1978), scale 1:125,000; Polenz and others (2004), scale 1:24,000; Brown (1970), scale 1:62,500; Cady, Sorensen and MacLeod (1972), scale 1:62:500; Cady, Tabor and others (1972), scale 1:62,500; Tabor and others (1972), scale 1:62:500.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Host rocks of manganese deposits of the Olympic Peninsula formed at an ocean ridge or in a back arc basin at the active margin of the North American plate (Garrison, 1973; Snavely, 1987, p. 306-309). Manganese deposits of the region are associated with spilites (Park, 1942, p. 311-312) and commonly are found with reddish pelagic limestone inter bedded with the basalt. Manganese mineralization may have formed as disseminated bodies of replacement origin or as volcanogenic exhalative bodies (Sorem and Gunn, 1967).
Deposits Crescent mine (MRDS dep_id: 10203729).
Evidence from mineral occurrences MRDS.
Geochemical evidence Unknown.
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Cover thickness and description Minimal Quaternary deposits in valleys.
Authors Laurel G. Woodruff, Daniel W. Eungard.
New data needs Geophysics, geologic characterization, and detailed mapping.
Geologic mapping and modeling needs Detailed geologic mapping.
Geophysical survey and modeling needs High-resolution, Rank 1 aeromagnetic and aeroradiometric surveys.
Digital elevation data needs Lidar is complete at QL3 to QL1 with most area covered by QL3.