Portland State University. Department of Earth Sciences
Marvin H. Beeson
Date of Publication
Master of Science (M.S.) in Geology
Bauxite -- Oregon -- Columbia County -- Analysis, Bauxite -- Washington (State) -- Wahkiakum County -- Analysis
1 online resource (ix, 87 pages) : illustrations
Wet chemical analysis and instrumental neutron activation analysis (INAA) were performed on a suite of samples from three residual ferruginous bauxite profiles in the study area for abundances of Al2O3,
SiO2, Fe2O3, Ti O2, Na, Sc, Hf, Cr, Co, La, Sm, Yb, Lu, and Th. In addition a mineralogical study accompanied this research, using petrographic, differential thermal, and x-ray diffraction techniques. In each profile, the relative mobility of these elements were calculated by empirical methods for comparison with the parent rock and mineral properties in the saprolite.
This study indicates that the first original constituent of the basalt to decompose under the influence of weathering is interstitial glass. The second phase results in the decomposition of plagioclase and pyroxene. Plagioclase alters mainly to kaolinite and metahalloysite. Pyroxene and basaltic glass alters mainly to nontronite, hematite, limonite, and amorphous clay. Opaques remain nearly unaltered. The low grade ferruginous bauxite ore is not derived solely from basalt, but also forms by weathering of younger sedimentary strata that overlie the basalt flows of the Columbia River Group. In general, components that are progressively depleted under the influence of weathering are Si02, Na, La, Sm, and Lu; these losses result in greater concentration of AlO3, Fe2O3, TiO2, Sc, Cr, Th, and Hf. Cobalt behaves erratically. There seems to be no predictable relationship between the ratios of rare earth elements in ferruginous bauxite and the parent rock. In the most weathered zone, Fe2O3, TiO2, Al2O3, Sc, Hi, Cr, and Th are enriched. Na, SiO2, Sm, and Lu are depleted relative to the parent rock. Trace elements associated with iron-rich pisolites are Lu, Yb, Th, and Co. Only Th is associated with gibbsite.
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Jackson, Ronald Laverne, "A Mineralogical and Geochemical Study of the Ferruginous Bauxite Deposits in Columbia County, Oregon, and Wahkiakum County, Washington" (1974). Dissertations and Theses. Paper 2133.