RARE EARTH ELEMENT MOBILITY IN A LATERITIC WEATHERING PROFILE, SALINE COUNTY, ARKANSAS

Rare Earth Elements (REEs) are an integral part of modern technology. Accessory minerals in alkaline igneous rocks are particularly enriched in REEs. Previous research by two of the authors confirmed that titanite/sphene and fluorapatite, in the nepheline syenite from this locality, contain appreciable REEs (Edge et al., 2018). We hypothesize that intense weathering of the nepheline syenite concentrated the REEs similar to supergene enrichment. We collected one inch core samples of unaltered nepheline syenite and grab samples every 1.5 meters up the weathering profile in an inactive open-pit bauxite mine during the Spring and Fall semesters of 2023. We prepared thin-sections of some samples and sent select samples to an accredited lab for analysis of 27 elements (including the REEs). Bulk sample analysis of the nepheline syenite give a LREE total of 871.9 µg/g and a HREE total of 116.9 µg/g. An iron oxide weathering rind immediately above the nepheline syenite yielded a LREE content of 1375.9 µg/g and 238.6 µg/g for the HREEs. The most heavily altered weathering material had a LREE total of 2052.3 µg/g and a HREE total of 1243.5 µg/g. Our data support the concentration of REEs in the weathering profile above the nepheline syenite.