Portland State University. Department of Geology
Michael L. Cummings
Date of Award
Master of Science (M.S.) in Geology
1 online resource (151 p.)
Metamorphism (Geology) -- Washington (State) -- Wind River Region, Hydrothermal deposits -- Washington (State) -- Wind River Region, Geochemistry -- Washington (State) -- Wind River Region, Geology -- Washington (State) -- Wind River Region
The Wind River gold prospect is located in TSN, R7E of Skamania County, Washington, and is an epithermal gold-quartz vein system hosted in volcanic rocks of the Ohanapecosh Formation, a late Eocene to middle Oligocene unit of calcalkaline chemical composition. Andesitic pyroclastic rocks of the Ohanapecosh Formation are the host of mineralization in the study area, and form the lowest of several stratigraphic subunits. These pyroclastic rocks are overlain by two sequences of lava flows which cap the ridges and are folded by an anticlinal warp over the length of Paradise Ridge, plunging gently to the southeast. Toward the west, the number of flows decreases and the proportion of intercalated pyroclastic rocks increases. Numerous dikes cut the pyroclastic rocks at the Wind River prospect. Geochemical data show these dikes to have been feeders for the overlying lava flows. Differing degrees of alteration of the dikes relative to the most intensely altered pyroclastic rocks which they cut indicates a complex history of overlapping hydrothermal and volcanic activity at the prospect.
McGowan, Krista I., "Geochemistry of alteration and mineralization of the Wind River gold prospect, Skamania County, Washington" (1985). Dissertations and Theses. Paper 3586.