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Northeastern Section (39th Annual) and Southeastern Section (53rd Annual) Joint Meeting (March 25–27, 2004)

Paper No. 2
Presentation Time: 1:00 PM-5:00 PM

GEOCHEMICAL AND MINERALOGIC ANOMALIES IN SOILS OVER HYDROTHERMALLY ALTERED ROCKS IN THE CAROLINA SLATE BELT, PILOT MOUNTAIN, NORTH CAROLINA


KIKUCHI, Asami1, WAMWEYA, Amos1 and NUSBAUM, Robert L.2, (1)Geology and Environmental Geosciences, College of Charleston, 58 Coming Street, Charleston, SC 29401, (2)Geology and Environmental Geosciences, College of Charleston, Charleston, SC 29424, asami2@yahoo.com

Hydrothermal alteration in the Carolina Slate Belt has been the subject of a variety of geochemical studies. Pilot Mountain in Randolph County, North Carolina, is made up of hydrothermally altered rock. The purpose of this research is to identify geochemical and mineralogical differences in soils at Pilot Mountain compared to those at a control site where alteration did not occur.

We analyzed nine Pilot Mountain soil samples and six from Morrow Mountain, North Carolina, as the control site. Our analysis included reflectance spectroscopy to identify phyllosilicates, carbonates, and iron oxides in the soils, and x-ray fluorescence spectrometry to delineate geochemical anomalies. Both mountains stand as topographic highs; Pilot Mountain due to high silica content associated with hydrothermal alteration, and Morrow Mountain due in part to its rhyolite cap, which overlies basalt. Although the nature of the Pilot Mountain bedrock prior to hydrothermal alteration is difficult to discern due to textural and compositional changes accompanying alteration, Schmidt (1985) proposed andesitic to dacitic composition. To approximate andesitic geochemistry for Morrow Mountain soils, we used average values from basalt and rhyolite data.

Pyrophyllite was detected in all Pilot Mountain soil samples in addition to kaolinite, or kaolinite-smectite mixtures. Reflectance spectra from Morrow Mountain soil samples vary with rock type. Basalt samples have weak kaolinite-smectite features along with calcite. Kaolinite-smectite mixtures are prominent in rhyolite samples. Hematite was identified in one of the rhyolite samples.

Pilot Mountain soil samples have elevated levels of tungsten, arsenic, and bismuth compared to our control site samples. Chromium was enriched in some of the Pilot Mountain samples. Manganese and zinc are depleted in Pilot Mountain soils that we analyzed. These results are consistent with intense hydrothermal alteration associated with gold and pyrophyllite mineralization in the Carolina Slate Belt.

Session No. 58--Booth# 48

T24. Undergraduate Research (Posters) II
Friday, 26 March 2004: 1:00 PM-5:00 PM
Geological Society of America Abstracts with Programs. Vol. 36, No. 2, p.124
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