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Placer platinum-group metals offshore of the Goodnews Bay Ultramafic Complex, Southwest Alaska.
NTIS: PB 88-251996, 1988; :1-60
In 1981 and 1985-86, the Bureau of Mines conducted orientation studies of marine placer platinum-group (PGM). PGM are derived from the Goodnews Bay Ultramafic complex, and magnetic surveys show that the complex extends offshore at least 4 miles. The present seafloor was an emergent foreland as recently as 8,000 yr ago. High-energy ocean processes are transporting and depositing sediment such that PGM-bearing materials are reworked and later masked by barren littoral drift. Exploration targets include placers formed since present transgression began and ancient marine and drowned fluvial deposits. Additionally, there is evidence of PGM solution transport and accretion. At least minor values of PGM in recent lag-type placers and possible submarine strands are concentrated along an offshore scarp incised through glacial deposits into the preglacial surface between Flat Cape and Red Mountain. Other recent PGM- bearing features include Flat Cape Shoal, Chagvan Bay, Salmon River delta, and modern beaches. Ancient placers include possible north- south fluvial systems 2 to 3 miles offshore, a nearshore scarp 50 ft below sea level, and strands adjacent to projected Ultramafic bedrock slopes. The existence of ancient placers is dependent on depth of glacial erosion.
Mining; Sea water; Geologic surveys; Geologic formations
NTIS Accession No.
NTIS: PB 88-251996
BoM Alaska Field Oper. Center
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division