Integrated mapping of rare earth element mineralization using hyperspectral imaging and laser induced fluorescence spectroscopy in drill cores from the Storkwitz Carbonatite, Germany

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Journal Title
Journal ISSN
Volume Title
Insinööritieteiden korkeakoulu | Master's thesis
Date
2023-12-11
Department
Major/Subject
European Mining Course
Mcode
Degree programme
European Mining, Minerals and Environmental Programme (EMMEP)
Language
en
Pages
78+1
Series
Abstract
The growing importance of rare earth elements (REEs) in sustainable technologies necessitates an efficient assessment of potential resource targets within the European Union. Traditional analytical techniques for REE determination have drawbacks like destructive and time-consuming sample preparation, but hyperspectral imaging (HSI) and laser-induced fluorescence (LiF) offer promising alternatives. This project aims to use a combined HSI and LiF method to qualitatively characterize REE mineralization and alteration in drill core samples from the Storkwitz deposit, Germany. The goal is to develop a transferrable mapping approach for REEs, while enhancing our understanding of the Storkwitz deposit. It aims to check the robustness of HSI conducted across the extended wavelength range as a tool in effectively characterizing the lithologies associated with REE mineralization in the Storkwitz breccia. It also tests if the combined HSI-LiF can provide new insights into the presence of REEs and its associated minerals in the Storkwitz breccia. The proposed workflow involves acquiring hyperspectral data of the Storkwitz drill core and block sections in three wavelength ranges (VNIR-SWIR, MWIR, and LWIR). Automatic and manual endmember extraction is performed on the smaller subsection of data to create spectral libraries, which are then used for spectral unmixing and mapping of the entire hyperspectral dataset to identify lithologies. LiF is used to identify and map rare earth elements (REEs) in selected REE-rich zones identified from the hyperspectral data. The results indicated that the Storkwitz Breccia is primarily composed of ankerite in the matrix, along with minor amounts of white mica, clay, iron oxides, and REE-fluorcarbonates. The breccia contains different clasts, including granitoid clasts rich in orthoclase and quartz-albite-biotite, as well as carbonatitic clasts dominated by ankerite, dolomite, and ankerite-calcite. The breccia also underwent four alteration phases, including fenitization, biotite alteration, white mica-clay alteration, and ferric alteration. Laser-induced spectroscopy confirmed the presence of REEs, with apatite and REE-fluorcarbonates, particularly bastnäsite, being the main REE-bearing minerals. The specific REEs identified include Nd3+, Sm3+, Pr3+, and possibly Eu3+. The comprehensive workflow combining hyperspectral imaging and laser-induced fluorescence spectroscopy proved to be a successful approach for characterizing lithologies and mapping rare earth element mineralization in the Storkwitz breccia. The study opens up new possibilities for efficient REE exploration in similar geological settings, providing valuable information for geological logging and interpretation.
Description
Supervisor
Leveinen, Jussi
Thesis advisor
Schmiedel, Tobias
Keywords
hyperspectral scanning, laser induced fluorescence,, spectroscopy, Storkwitz breccia, rare earth elements
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