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

From ore materials to precious gemstones, minerals play an important role in almost every aspect of our lives. This session will focus on characterization of economic minerals employing spectroscopic techniques, geochemical analysis, and microanalytical techniques.

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Assessing the Suitability of Natural Scheelites for In Situ REE Analysis and Ore Geochemistry

Paper number: 113-9
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Scheelite, CaWO4, is a rare-earth-element (REE)-enriched accessory mineral found in ore deposits with the capacity to incorporate REEs, molybdenum, and uranium, making it a valuable geochemical proxy for understanding mineralization and critical mineral potential.   Despite advances in in-situ trace element analysis, the absence of a well-characterized, widely available scheelite reference material (RM) hinders interlaboratory reproducibility and method validation of in situ trace element analyses.   Five natural scheelite samples from four geologically distinct localities:  Stibnite Yellow Pine (NMNH-4, Idaho, USA), Victory South–McLeay (Australia), Yaogangxian (South China), and Xuebaoding (Sichuan, China) were assessed for REE and U concentrations along with homogeneity and precision, both within and between discrete crystals.  Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry analysis reveals distinct REE and trace element patterns that differentiate the scheelites by deposit type: Four distinct REE profiles were observed: (1) bell-shaped with a positive Eu anomaly and MREE enrichment, (2) LREE enriched and HREE depletion with a negative Eu anomaly, (3) HREE-enriched with a positive Eu anomaly, La enrichment and Ce depletion, and (4) flat with a positive Eu anomaly, La enrichment and Ce depletion in the rim, and the inverse pattern in the core. Scheelite NMNH-4, a primary RM for in situ U-Pb dating, has high U (~21 ppm) but poor spot reproducibility for U (119% RSD) and REEs (300–400% RSD), low REE content (e.g., 2.9 ppm La, 7.0 ppm Ce, 1.4 ppm Yb, 0.14 ppm Lu), and strong core-rim zonation, limiting its use for trace element calibration. In contrast, natural scheelites, Xueboading 5 (0.14 ppm U, 87.0 La, 241.5 Ce, 19.8 Yb, 2.02 Lu, 20–60% RSD), Xueboading 6 (0.59 U, 17.8 La, 43.5 Ce, 45.0 Yb, 7.22 Lu, 50–150% RSD), and Yaogangxian (0.36 U, 14.3 La, 39.0 Ce, 124.05 Yb, 18.1 Lu, 20–100% RSD), exhibit lower U,  improved analytical precision and minimal core to rim zoning. With further screening of specific grains, they are possible candidates for REE and U RMs.  In particular they may be suitable as secondary RMs for interlaboratory reproducibility and method validation in conjunction with synthetic scheelites (Zhang et al., 2023 doi: 10.1111/ggr.12523), used as primary RMs, which are more homogeneous (0.5-5.6% RSD for REE) but have more limited supplies.

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

doi: 10.1130/abs/2025AM-413166

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