113-9 Revealing Rare Earth Elements (REEs) Enrichment: An Example from Garnet Amphibolite

Session: Mineralogical Characterization of Economic Resources: From Critical Minerals to Gemstones (Posters)

Poster Booth No.: 254

Presenting Author:

Mia Enders

Authors:

Enders, Mia Allyn¹, Lahiri, Nabajit², Stanfield, C. Heath³, Teng, Yuntian⁴, Mergelsberg, Sebastian⁵, Miller, Quin⁶, Massonne, Hans-Joachim⁷, Schaef, H. Todd⁸, Cao, Wentao⁹

(1) SUNY Fredonia, Fredonia, NY, USA, (2) Pacific Northwest National Laboratory, Richland, WA, USA, (3) Pacific Northwest National Laboratory, Richland, WA, USA, (4) Pacific Northwest National Laboratory, Richland, WA, USA, (5) Pacific Northwest National Laboratory, Richland, WA, USA, (6) Pacific Northwest National Laboratory, Richland, WA, USA, (7) Fakultät Chemie, Universität Stuttgart, Stuttgart, Germany; School of Earth Sciences, China University of Geosciences, Wuhan, China, (8) Pacific Northwest National Laboratory, Richland, WA, USA, (9) SUNY Fredonia, Fredonia, NY, USA,

Abstract:

Rare Earth Elements (REEs) have a significant impact on economics and energy security, influencing everyday life through their involvement in electronics, vehicles, and other technologies. These elements are typically extracted from REE-enriched specimens, such as carbonatite or ion-adsorption clays. However, textures and varieties of REE-bearing minerals in geological specimens are typically complex, rendering the difficulty in studying and selecting a suitable REE extraction approach. We utilized a variety of instruments with corresponding applications to reveal REE-bearing minerals in a rare REE-enriched garnet amphibolite. Wavelength Dispersive (WD) X-ray fluorescence spectroscopy (XRF) reveals that the specimen is enriched with REEs, comparable to some REE ores, with a negative Ce anomaly. X-ray microtomography (XMT) shows that the higher-density minerals are spatially distributed as connected or individual minerals, accounting for 2.65 vol% of all minerals. Micro-XRF maps of multiple elements indicate the correlation of REE positions with phosphorus. This was confirmed under a higher magnification showing the high concentrations of phosphorus and oxygen with REEs. Energy dispersive X-ray spectroscopy via scanning electron microscope (SEM-EDS) confirms the presence of lanthanide phosphates and yttrium phosphates, with the REE phosphates distributed as anhedral to subhedral grains or along grain boundaries or cracks. Wide Angle X-ray Scattering (WAXS) of the billets revealed signatures consistent with the presence of rhabdophane and xenotime. The spatial distribution, textural relationships, and alteration of mineral assemblages indicate the REE minerals were likely formed due to hydrothermal precipitation at shallow subsurface conditions. Despite the possible complexity of REE mineral occurrences in geological specimens, the multimodal approach is effective in revealing their mineral chemistry and structural information, which provides crucial basic information to apply extraction methods for the next step.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8268

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