General theme: Ore-formation models are developed which allow defining exploration tools, such as geochemical vectors and mineral pathfinders, which can in turn be applied to identify new target areas, like stratigraphic or structural traps. Research focusses on both field work and the integration of analytical techniques such as petrographic, mineralogical and geochemical analyses. This advanced characterisation on a macro- and micro-scale is applied on primary and secondary resources, as a first step in the extraction and recovery of base and critical elements. Due to the often complex mineralogy and/or low content of (critical) metals in primary (minerals, rocks…) and secondary resources (slags, ashes, sludges, concentrates…), a combination of advanced characterisation techniques (e.g. Raman, µ-XRF, LA-ICP-MS, FEG-EPMA, QXRD…) allows to obtain information on both the quantity and distribution of the elements and minerals of interest. This information is for example key to understand and optimise the metal recovery efficiency through particular processes (chemical digestion, thermal treatment….) and to efficiently develop valorisation routes for the residual fractions (see Research Line 4).
Metallogenic models are constructed which are used in the exploration of ore deposits. Two flagship deposits SIM² KU Leuven is currently working on, are: (1) Sediment-hosted Cu-Co deposits in the Central African Copperbelt. The origin of the metals and fluids, the precipitation conditions and the timing of ore formation are integrated in a metallogenic model which allows to constrain target areas for exploration. 2- and 3D models of the ore are constructed to allow exploration at the mine scale and facilitate exploitation; (2) Pegmatite hosted Ta-Sn-W ore deposits quartz vein Sn-W-Au deposits in the Karagwe-Ankole belt (Central Africa). Spatial distribution models of pegmatites and quartz veins combined with newly developed ore-forming models are used to define the control on the occurrence of these ore deposits. The ore-forming models are developed based on extensive field work, mineral and rock characterisation, micro-analytical geochemistry (Raman, LA-ICP-MS and FEG-EPMA) and numerical modelling.
2D and 3D models of the spatial, chemical and mineralogical variability of tailings are developed in combination with quantitative characterisation and distribution analysis of base and critical elements. The most appropriate dissolution method, and if needed, enrichment method for the quantification of the total concentration of the elements is elaborated. The analytical set-up and standardisation and calibration method are optimised. The detailed distribution and the relationship of the ore and host-rock minerals is visualised by optical microscopy, particle mapping analysis (PMA) by the mineral liberation analysis (MLA technology) and by micro-XRF. Both total and sequential extraction, as well as mineralogical characterisation, are used to infer the solid-phase speciation of the elements of interest.
For low grade ores or residues or for complex End-of-Life products, the use of FEG-EPMA-WDS (Field Emission Gun Electron Probe Micro Analysis – Wavelength Dispersive Spectroscopy) is being applied to quantify based on standards, the concentration of the elements of interest (by point analyses) and their distribution among the phases (by elemental mapping) at the µ-level. Compared to Energy Dispersive Spectroscopy (EDS), WDS has a higher spectral resolution, which allows to differentiate elements with overlapping EDS lines, such as is the case for the REE elements. As such, REE elements, precious metals or (other) critical metals are investigated with FEG-EPMA in slags, sludges… . The FEG-EPMA technique is complimentary to other techniques, such as Raman microscopy, QXRD (mineral quantification) or Mössbauer (chemical bonding), to obtain a complete picture of the material. This information is then valuable in the design of processes to recover the elements of interest or to create a product with the desired properties.