Date of Award

Fall 12-16-2024

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

W. Crawford Elliott

Second Advisor

Yuanzhi Tang

Abstract

Cretaceous kaolins (Sandersville, GA) and bauxite-kaolins (Andersonville, GA) of the Southeast Upper Coastal Plain were found as novel rare-earth element (REE) resources. These REE resources were found in mine tailings, the sand fractions of mined kaolin ores, and interbedded sands with mined kaolin ores. The tailings were enriched in heavy REE (HREE). The kaolins, their clay fractions, and the interbedded sands were enriched in the light REE (LREE). Secondary weathering processes (diagenesis) produced secondary xenotime overgrowths in the sand fractions of the Cretaceous kaolins in addition to the already known secondary LREE phosphates found in the clay fractions of these kaolins. Xenotime (HREE) and monazite (LREE) were the primary sources of REE found in the kaolin mine tailings and sands.

Ion-exchangeable REE were not found in these kaolins. However, significant fractions (11-36%) of the REE were ion-exchangeable on mineral surfaces in the bauxite-kaolins. The greatest amounts of sorbed REE were found in the kaolinite-rich horizons underlying the bauxite zone in the bauxite-kaolin section. Unlike the kaolin deposits lacking bauxite zones, the REE were mobilized from the bauxite zone and accumulated as sorbed ions in the underlying lower kaolin strata. This deposit scheme may be viewed as a hypothetical model for predicting the occurrence of REE in similar bauxite-kaolin sections elsewhere in the region. These findings are particularly stimulating considering the critical nature of these REE. This study provides a basis for future exploration of kaolin mine tailings, interbedded sands, and bauxites in the Southeast Upper Coastal Plain.

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