Non-systematic weathering profile in the Blue Ridge Mountains, N. C. : Role of geochemical variables

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5690774

Ciampone, M A; McVey, D E; Gerke, T L; Briggs, W D; Zhang, Yangsheng; Maynard, J B; Huff, W D ^[1]

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1. Univ. of Cincinnati, OH (United States). Dept. of Geology

Weathering profiles from representative cores of the Coweeta Group, schist, and Tallulah Falls Fm, gneiss, in the Blue Ridge Mountains of North Carolina were examined. The predominant alteration minerals, which formed from the partial alteration of biotite and plagioclase, include kaolinite, chlorite, vermiculite interstratified with biotite, gibbsite. These mineral phases were identified using petrographic observation, SEM, X-ray diffraction, and selected electron microprobe analysis. These minerals commonly represent a weathering profile (developed from surface to depth on a single source rock) ranging from mature (gibbsite), to intermediate (kaolinite + interlayered biotite/vermiculite), to immature (plagioclase + biotite) at depth. In this study, however, there is no clear vertical zonation of the weathering profile. This indicates a more selective weathering process than would typically be assumed. This nonsystematic weathering profile may reflect variations in bulk composition of the parent rock and/or variations in the composition of ground water. The presence and abundance of gibbsite in these weathering profiles is unusual because it is normally associated with bauxite in which the Al[sub 2]O[sub 3] content is > 80 wt.%. In this study the Al[sub 2]O[sub 3] content of the regolith is approximately 20 wt.%. The presence of gibbsite emphasizes the importance of solution-reprecipitation of Al-rich phases as an independent process in temperature climates, and suggests the activity of silica is more critical than regional climatological effects in controlling regolith formation.

• OSTI ID: 5690774
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALUMINIUM COMPOUNDS
ALUMINIUM HYDROXIDES
CHEMISTRY
DEVELOPED COUNTRIES
GEOCHEMISTRY
GIBBSITE
HYDROGEN COMPOUNDS
HYDROXIDES
MINERALOGY
MINERALS
MOUNTAINS
NORTH AMERICA
NORTH CAROLINA
OXIDE MINERALS
OXYGEN COMPOUNDS
PHASE STUDIES
USA
WEATHERING