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Geologic and Geochemical Investigation of the "Nail" Allochthon, East-Central Alaska.
For Reference Only At Bureau Libraries :26 pages
The "nail" Allochton, east-central Alaska, was investigated by the Bureau of Mines in cooperation with the state of Alaska, Div. of Geological and Geophysical Surveys', as part of an effort to develop more definitive information on Alaska's critical and strategic mineral reserves. The peridotites and former peridotites in the vicinity of the vertical angle bench mark nail constitute an approximately 8-mile-long, 2,000-ft-thick trust sheet of probable Permian age that overlies a complex assemblage of Paleozoic(?) Greenschist-Facies metamorphic rocks. An extensive zone of carbonate alteration is present at the base of the Ultramafic thrust sheet. The mineralized zone contains up to 17 pct mgo. The remote location and inaccessibility of the zone render it subeconomic at this time. Although the periodotites at nail ridge usually contain 2 to 4 pct chromite, metallurgical tests by the Bureau's Albany Research Center indicate it to be a high-magnesium, high-aluminum chromite of submarginal grade. Neither platinum-group metals nor gold in significant amounts are present either in the bedrock or as placer concentrations in the streams draining the study area.
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Alaska Field Operations Center
Page last reviewed: March 11, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division