Portland State University. Department of Geology
Michael L. Cummings
Date of Publication
Master of Science (M.S.) in Geology
Bauxite -- Oregon -- Columbia County, Iron ores -- Oregon -- Columbia County
1 online resource (138 p.)
Two major theories have been advanced to account for the scattered distribution of ferruginous bauxite deposits. Original workers proposed that ferruginous bauxite originally developed over all exposed Columbia River Basalt in western Oregon and was subsequently removed by erosion. Studies which followed have suggested that it may be locally favorable conditions, especially of drainage, which are responsible for deposit distribution. Field mapping in the Chapman Quadrangle shows a possible correlation between a series of sheared zones, which may have improved drainage, and the distribution of ferruginous bauxite deposits. Examination of the pisolitic zone ferruginous bauxite of the Chapman Quadrangle failed to show any evidence supporting the theory that this zone was produced by fluvial action. It appears, instead that the pisolitic zone of the deposits studied developed in place and that the structures seen in this zone are the result of authigenic processes. Mineralogical study of samples from the Chapman Quadrangle suggests that the ferruginous bauxite of the area probably developed under slightly acidic pH conditions and that the assemblage quartz, kaolinite, gibbsite may exist in ferruginous bauxite deposits because of the presence of iron oxide and hydroxide coatings on the quartz which may cut off contact between quartz and gibbsite. Chemical study shows that the lateral variation in elemental concentrations is much less than the vertical variation in concentrations seen by some previous workers, and that lateral variation appears to be randomly distributed for most elements. The behavior of elements during weathering can best be modeled by taking into account the various sorbtive reactions between ions formed during weathering and clays and hydroxides.
Marty, Richard Charles, "Formation and zonation of ferruginous bauxite deposits of the Chapman quadrangle, Oregon" (1983). Dissertations and Theses. Paper 3513.