SEM-Based Automated Mineralogy and Its Application in Geo- and Material Sciences

Abstract

Scanning electron microscopy based automated mineralogy (SEM-AM) is a combined analytical tool initially designed for the characterisation of ores and mineral processing products. Measurements begin with the collection of backscattered electron (BSE) images and their handling with image analysis software routines. Subsequently, energy dispersive X-ray spectra (EDS) are gained at selected points according to the BSE image adjustments. Classification of the sample EDS spectra against a list of approved reference EDS spectra completes the measurement. Different classification algorithms and four principal SEM-AM measurement routines for point counting modal analysis, particle analysis, sparse phase search and EDS spectral mapping are offered by the relevant software providers. Application of SEM-AM requires a high-quality preparation of samples. Suitable non-evaporating and electron-beam stable epoxy resin mixtures and polishing of relief-free surfaces in particles and materials with very different hardness are the main challenges. As demonstrated by case examples in this contribution, the EDS spectral mapping methods appear to have the most promising potential for novel applications in metamorphic, igneous and sedimentary petrology, ore fingerprinting, ash particle analysis, characterisation of slags, forensic sciences, archaeometry and investigations of stoneware and ceramics. SEM-AM allows the quantification of the sizes, geometries and liberation of particles with different chemical compositions within a bulk sample and without previous phase separations. In addition, a virtual filtering of bulk particle samples by application of numerous filter criteria is possible. For a complete mineral phase identification, X-ray diffraction data should accompany the EDS chemical analysis. Many of the materials which potentially could be characterised by SEM-AM consist of amorphous and glassy phases. In such cases, the generic labelling of reference EDS spectra and their subsequent target component grouping allow SEM-AM for interesting and novel studies on many kinds of solid and particulate matter which are not feasible by other analytical methods.

The birth of the Alps: Ediacaran to Paleozoic accretionary processes and crustal growth along the northern Gondwana margin

“…For the evaluation of the mineral modes and detrital zircon 2D geometrical properties, polished thin sections from the samples were analysed by automated SEM Automated Mineralogy methods (Schulz et al 2020). The measurement routine XMOD is a single spot point counting for mineral mode analysis, based on ~ 10 5 EDS spectra at a 10 µm step size in a thin section.…”

Monazite Microstructures and Their Interpretation in Petrochronology

“…Thus, for search and petrographic documentation of monazite in thin sections, the scanning electron microscope (SEM) is essential. Automated mineralogical methods (e.g., Schulz et al, 2020), based on an SEM equipped with image analysis software, an automated steering of the electron beam, and energy dispersive spectrometers for EDS analyses, can be applied to thin sections of potentially monazitebearing rocks. Software packages for mineral liberation analysis (MLA versions 2.9 or 3.1 and QEMSCAN by FEI Company) or alternative software platforms by Zeiss Mineralogic Systems and TESCAN TIMA can then be used for the automated steerage of the electron beam for EDS identification of mineral grains and the collection of EDS spectra.…”

“…Parts of such large monazites can show variable Th contents and traces of alteration with tiny holes along cracks, so that domains for reference measurements should be carefully selected (Figures 2c,d). However, it is important to emphasize that natural reference monazites involved in the FIGURE 1 | Search for monazite by scanning electron microscopy automated mineralogy methods (e.g., Schulz et al, 2020). (A) Merged frame view of a rare phase search measurement routine applied to a polished thin section.…”

Editorial for Special Issue “Applications of SEM Automated Mineralogy: From Ore Deposits over Processing to Secondary Resource Characterization”

“…For the presentation of the potential of SEM-AM to a broader audience, a review contribution is needed. That is provided by Schulz et al [12], entitled "SEM-Based Automated Mineralogy and its Application in Geo-and Material Sciences". It presents an overview of the SEM-AM measurement routines and their implementation in the available software platforms.…”

“…An answer to the challenges is the development of SEM-AM, an analytical tool combining software for BSE image examination, with more important specific steering control of the electron beam for EDS spectral analyses. Different classification algorithms and four principal SEM-AM measurement routines for point counting modal analysis, particle analysis, sparse phase search and EDS spectral mapping are offered by the relevant software providers [1,[10][11][12]. These measurement routines provide the potential for the SEM-AM applications to scientific topics outside of the raw materials processing chain [13][14][15][16][17][18].…”