White River

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

Information leading to the delineation of this focus area

Basis for focus area Area delineated by large mapped areas of alunite-rich advanced argillic and residual quartz alteration (John and others, 2003; Blakely and others, 2007) underlain by partly drilled porphyry Cu mineralization; 1 km buffer around mapped alteration.
Identified resources Identified resources for aluminum (alunite). Historical production of aluminum (alunite) and silica.
Production Significant silica produced from 1987 to present; minor production from 1930s to 1948.
Status Past mining. Active silica mining; past exploration for high sulfidation Au-Ag, lithocap alunite, and porphyry Cu mineralization.
Estimated resources Early 1940s resource estimate of 1.14 Mt rock containing >20% alunite; 20-year resource at Scatter Creek quarry when it opened in 1999.
Geologic maps Tabor and others (2000), scale 1:100,000; John and others (2003), scale ~1:40,000; Blakely and others (2007), scale ~1:65,000; McCulla (1986), scale unknown.
Geophysical data Adequate aeromagnetic coverage. Inadequate aeroradiometric coverage. Blakely and others (1999, 2007) provide detailed regional aeromagnetics and gravity data.
Favorable rocks and structures Silicified and altered volcanic rocks of the early Miocene Fifes Peak Formation. These rocks host a structurally controlled zone of intense acid-sulfate alteration leaching primary elements leaving a residuum Si/Al caprock. This deposit bears striking similarity to the Goldfield deposit of Nevada, however a polymetallic system at depth has yet to be identified.
Deposits Enumclaw alunite prospect (White River alunite deposits) (MRDS dep_id: 10135527).
Evidence from mineral occurrences MRDS; John and others (2003); Blakely and others (2007).
Geochemical evidence Geochemical summary in John and others (2003).
Geophysical evidence See Blakely and others (2007) for interpretation of detailed aeromagnetic and gravity data.
Evidence from other sources Drilling by Kennecott in mid-2000s intersected porphyry copper mineralization at shallow depths but drilling was not sufficient to define potential resources.
Comments Area is heavily forested tree farm with several active/recently active silica quarries; exposures are mostly residual quartz alteration or manmade. Mostly private and some state (mineral lease) ownership. Future mineral development may be possible but anticipate significant opposition as it is in a watershed of a major population center.
Cover thickness and description Exposed at the surface.
Authors Daniel W. Eungard.
New data needs High resolution geophysics; develop deposit model, lidar.
Geologic mapping and modeling needs Mapping complete; deposit model.
Geophysical survey and modeling needs High resolution aeromagnetic and aeroradiometric survey. Gravity also inadequate, a state-led ground based study is possible, low density deposits at surface and suspected high density deposits at depth would be well resolved with gravity.
Digital elevation data needs Lidar planned/funded in northern part of focus area; incomplete in southern portion.