Characterization of regolith-hosted rare earth element deposits using reflectance spectroscopy: Framework towards an efficient and reliable field exploration tool

IF 3.4 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Journal of Geochemical Exploration Pub Date : 2024-09-03 DOI:10.1016/j.gexplo.2024.107578

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引用次数: 0

Abstract

With a growing demand for the rare earth elements (REE), exploration of regolith-hosted REE resources worldwide has been thriving in recent years and development of a rapid and reliable field-based tool will greatly facilitate the survey and exploration. In this study, we use visible and short-wave infrared (VNIR-SWIR) reflectance spectroscopy to comprehensively evaluate the applicability of the technique to explore regolith-hosted REE resources, exemplified by three representative regolith-hosted REE deposits in China. Neodymium among the REE shows reliably detectable spectral features in the VNIR-SWIR spectroscopy down to concentrations of 10–50 ppm in field samples with heterogeneous mineral grain sizes. The Nd spectral intensity of electronic transition at the band of ∼800 nm is correlated with bulk Nd concentrations and can be used as semi-quantitative indicators for the Nd concentrations, thereby the total REE in regolith. Moreover, VNIR-SWIR spectroscopy is demonstrated to be capable of delineating favorable ore-bearing mineralogy by characterizing the abundance and type of clay minerals and Fe (oxyhydr)oxides, and the crystallinity of kaolinite-group minerals. However, the Nd spectral features of samples with high bulk Fe₂O₃ contents (>3 wt%) are significantly masked due to overlapping by the strong absorption features of ferric (oxyhydr)oxides. VNIR-SWIR spectroscopy is deemed to be applicable to the exploration of regolith-hosted REE resources developed from Fe-poor felsic rocks.

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利用反射光谱鉴定沉积岩型稀土元素矿床的特征：高效可靠的实地勘探工具框架

随着对稀土元素（REE）需求的不断增长，近年来全球范围内对雷公岩赋存 REE 资源的勘探蓬勃发展，开发一种快速可靠的野外工具将极大地促进勘查和勘探工作。本研究利用可见光和短波红外（VNIR-SWIR）反射光谱技术，全面评估了该技术在勘探残积岩型 REE 资源方面的适用性，并以中国三个具有代表性的残积岩型 REE 矿床为例。在具有不同矿物粒度的野外样品中，REE 中的钕在 VNIR-SWIR 光谱中显示出可靠的可探测光谱特征，浓度低至 10-50 ppm。800 纳米波段电子转变的钕光谱强度与块体钕浓度相关，可用作钕浓度的半定量指标，进而确定摄影岩中的 REE 总量。此外，VNIR-SWIR 光谱法通过表征粘土矿物和铁（氧氢）氧化物的丰度和类型以及高岭石类矿物的结晶度，被证明能够划分出有利的含矿矿物学。然而，Fe2O3 体积含量高（3 wt%）的样品的钕光谱特征由于与铁（氧化）氧化物的强吸收特征重叠而被严重掩盖。VNIR-SWIR 光谱法被认为适用于勘探从贫铁长英岩中开发出来的再结晶寄存 REE 资源。

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来源期刊

Journal of Geochemical Exploration 地学-地球化学与地球物理

CiteScore

7.40

自引率

7.70%

发文量

148

审稿时长

8.1 months

期刊介绍： Journal of Geochemical Exploration is mostly dedicated to publication of original studies in exploration and environmental geochemistry and related topics. Contributions considered of prevalent interest for the journal include researches based on the application of innovative methods to: define the genesis and the evolution of mineral deposits including transfer of elements in large-scale mineralized areas. analyze complex systems at the boundaries between bio-geochemistry, metal transport and mineral accumulation. evaluate effects of historical mining activities on the surface environment. trace pollutant sources and define their fate and transport models in the near-surface and surface environments involving solid, fluid and aerial matrices. assess and quantify natural and technogenic radioactivity in the environment. determine geochemical anomalies and set baseline reference values using compositional data analysis, multivariate statistics and geo-spatial analysis. assess the impacts of anthropogenic contamination on ecosystems and human health at local and regional scale to prioritize and classify risks through deterministic and stochastic approaches. Papers dedicated to the presentation of newly developed methods in analytical geochemistry to be applied in the field or in laboratory are also within the topics of interest for the journal.