The Potential of Reflectance and Laser Induced Luminescence Spectroscopy for Near-Field Rare Earth Element Detection in Mineral Exploration

Lorenz, Sandra; Beyer, Jan; Fuchs, Margret C.; Seidel, Peter; Turner, David P.; Heitmann, Johannes; Gloaguen, Richard

doi:10.3390/rs11010021

Cited by 17 publications

(24 citation statements)

References 42 publications

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“…532 nm) (e.g. Reisfeld et al, 1996;Gaft et al, 2005;Friis et al, 2010;Lorenz et al, 2019). Our results agree to those investigations and further highlight the specific drawbacks of non-suitable excitation conditions.…”

Section: Ree Reference Spectra At 532 Nm Laser Excitationsupporting

confidence: 91%

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A spectral library for laser-induced fluorescence analysis as a tool for rare earth element identification

Fuchs¹,

Beyer²,

Lorenz³

et al. 2020

Preprint

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Abstract. With the recurring interest on rare-earth elements (REE), laser-induced fluorescence (LiF) may provide a powerful tool for their rapid and accurate identification at different stages along their value chain. Applications to natural materials such as rocks could complement the spectroscopy-based toolkit for innovative, non-invasive exploration technologies. However, the diagnostic assignment of detected emission lines to individual REE remains challenging, because of the complex composition of natural rocks in which they can be found. The resulting mixed spectra and the large amount of data generated demand for automated approaches of data evaluation, especially in mapping applications such as drill core scanning. LiF reference data provide the solution for robust REE identification, yet they usually remain in the form of tables of published emission lines. We show that a complete reference spectra library could open manifold options for innovative automated analysis. We present a library of high-resolution LiF reference spectra using the Smithsonian rare-earth phosphate standards for electron microprobe analysis.We employ three standard laser wavelengths (325 nm, 442 nm, 532 nm) to record representative spectra in the UV-visible to near-infrared spectral range (340–1080 nm). Excitation at all three laser wavelengths yielded characteristic spectra with distinct REE-related emission lines for EuPO4, TbPO4, DyPO4 and YbPO4. In the other samples, the high-energy excitation at 325 nm caused unspecific, broadband defect emissions. Here, lower energy laser excitation showed successful for suppressing non-REE-related emission. At 442 nm excitation, REE-reference spectra depict the diagnostic emission lines of PrPO4, SmPO4 and ErPO4. For NdPO4 and HoPO4 most efficient excitation was achieved with 532 nm. Our results emphasise on the possibility of selective REE excitation by changing the excitation wavelength according to the suitable conditions for individual REEs. Our reference spectra provide a database for transparent and reproducible evaluation of REE-bearing rocks. The LiF spectral library is available at https://zenodo.org/ and the registered DOI: http://doi.org/10.5281/zenodo.4054606 (Fuchs et al., 2020). It gives access to traceable data for manifold further studies on comparison of emission line positions, emission line intensity ratios and splitting into emission line sub-levels or can be used as reference or training data for automated approaches of component assignment.

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Section: Ree Reference Spectra At 532 Nm Laser Excitationsupporting

confidence: 91%

“…Application of the presented LiF spectral library for REE identification in a natural mineral, xenotime from Novo Horizonte, sample NHJ (seeTurner (2015) andLorenz et al (2019)) …”

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confidence: 99%

A spectral library for laser-induced fluorescence analysis as a tool for rare earth element identification

Fuchs¹,

Beyer²,

Lorenz³

et al. 2020

Preprint

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“…Additionally, the absorption features at Siilinjärvi were noticeably deeper than at Marinkas Quellen. The double absorption features at 740 and 750 nm seen at Siilinjärvi at locations 2 and 3, and at location 6 of Marinkas Quellen can be attributed to a typical Dysprosium (Dy) absorption feature close to Nd 10 .…”

Section: Resultsmentioning

confidence: 98%

“…We selected two different flight altitudes in order to test the REE mapping capabilities with varying pixel sizes. The integration time of the sensor at both sites was set to 10 ms and the signal-to-noise ratio (SNR) of the sensor is 150:1 10 . We selected spectral sampling intervals of 5 nm at Marinkas Quellen and 8 nm at Siilinjärvi with a spectral resolution of 15 nm.…”

Section: Methodsmentioning

confidence: 99%

“…Neodymium (Nd) has some of the most pronounced absorption features among the REEs and therefore can be used as a key pathfinder element for REEs as a whole 9 . Nd has characteristic absorption features in the Visible to Near-Infrared (VNIR) range of the electromagnetic spectrum at 580 nm, 750 nm and 800 nm 10 . Turner et al 11 , Boesche et al 12 and Neave et al 9 successfully identified and mapped REEs using laboratory-or ground-based hyperspectral imaging (HSI).…”

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confidence: 99%

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Detection of REEs with lightweight UAV-based hyperspectral imaging

Booysen

Jackisch

Lorenz

et al. 2020

Sci Rep

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Rare earth elements (REEs) supply is important to ensure the energy transition, e-mobility and ultimately to achieve the sustainable development goals of the United Nations. Conventional exploration techniques usually rely on substantial geological field work including dense in-situ sampling with long delays until provision of analytical results. However, this approach is limited by land accessibility, financial status, climate and public opposition. Efficient and innovative methods are required to mitigate these limitations. The use of lightweight unmanned aerial vehicles (UAVs) provides a unique opportunity to conduct rapid and non-invasive exploration even in socially sensitive areas and in relatively inaccessible locations. We employ drones with hyperspectral sensors to detect REEs at the earth’s surface and thus contribute to a rapidly evolving field at the cutting edge of exploration technologies. We showcase for the first time the direct mapping of REEs with lightweight hyperspectral UAV platforms. Our solution has the advantage of quick turn-around times (< 1 d), low detection limits (< 200 ppm for Nd) and is ideally suited to support exploration campaigns. This procedure was successfully tested and validated in two areas: Marinkas Quellen, Namibia, and Siilinjärvi, Finland. This strategy should invigorate the use of drones in exploration and for the monitoring of mining activities.

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Analysis of deep-ocean sediments from the TAG hydrothermal field (MAR, 26° N): application of short-wave infrared reflectance (SWIR) spectra for offshore geochemical exploration

2020

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Purpose The cost-efficient methods of analysis, such as rapid short-wave infrared (SWIR) spectral 15 analysis have been applied for the efficient exploration of critical raw materials (CRM), including mineral 16 components and rare earth elements (REE) from the deep-ocean sediments. 17 Methods Gravity cored sediment samples were collected during an oceanographic mission to the Trans-18 Atlantic Geotraverse (TAG) hydrothermal field of the Mid-Atlantic Ridge (MAR, 26°N). SWIR reflectance 19 spectra (dependent variable) of samples were mathematically tested against referent geochemical data 20 (independent variable), obtained by conventional analysis (ICP/OES, ICP/MS), after applied full cross-21 validation multivariate partial least square regression (CVPLSR). Value of parameter -residual predictive 22 deviation (RPD) was used for evaluation of CVPLSR modeling: RPD > 2.5 (satisfactory calibration model 23 for the screening purposes), and RPD > 5.0 (model adequate for the quality control of the studied elements). 24 Results The CVPLSR modeling provided significant results for the determination of several mineral 25 components: major elements (Fe, and Si) had the values of RPD equal to 3.65 and 2.84, respectively 26 indicated a viable potential for their routine analysis, whereas RPD for Ca was equal to 5.51, thus assured 27 its quality control by SWIR analysis, in sediment samples of studied location. Among the REE, Ce (RPD 28 = 2.55) and Er (RPD = 2.59) yielded the most satisfactory results. 29 Conclusions The findings highlight the benefit of rapidly obtained empirical SWIR-reflectance data, 30 which can be used for near-real-time exploration of geochemical deposits hosted in deep-ocean sediments. 31 32 Keywords TAG hydrothermal field • Deep-ocean sediments • Rare earth elements (REE) geochemistry • 33 Short-wave infrared (SWIR) spectra • Cross-validation partial least square regression (CVPLSR) • Residual 34 predictive deviation (RPD) 35 36 1 Introduction 37 38 Current technological demands are rapidly increasing the global needs for critical raw materials (CRM), 39 including mineral components and rare earth elements (REE), that are generally in short supply, particularly 40 in Europe (Coulomb et al. 2015; Blengini et al. 2017). According to the most recent data of the European 41 Commission (EC), in 2017 the CRM including both light (La-Sm), and heavy rare earth elements (Eu-Lu) 42 together with Y, were listed with a maximum supply risk (EC 2017). The parameter 'substitution index' 43 defined in the EC report as a measure of difficulty in substituting the material, was scored (for both 44 economic importance and supply risk) with the highest values (0.9 -1.0) for all REE. At the same time, 45 China as a monopoly producer of the REE is the major consumer of these materials resulting in a danger to 46 the secure supply to the European industry. This fact together with the critical role of rare earths application 47 in the industry, technology, and medicine, created an urgent need for rapid exploration of natural ...

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The Potential of Reflectance and Laser Induced Luminescence Spectroscopy for Near-Field Rare Earth Element Detection in Mineral Exploration

Cited by 17 publications

References 42 publications

A spectral library for laser-induced fluorescence analysis as a tool for rare earth element identification

A spectral library for laser-induced fluorescence analysis as a tool for rare earth element identification

Detection of REEs with lightweight UAV-based hyperspectral imaging

Analysis of deep-ocean sediments from the TAG hydrothermal field (MAR, 26° N): application of short-wave infrared reflectance (SWIR) spectra for offshore geochemical exploration

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