A multimodal microcharacterisation of trace‐element zonation and crystallographic orientation in natural cassiterite by combining cathodoluminescence, EBSD, EPMA and contribution of confocal Raman‐in‐SEM imaging

Abstract

In cassiterite, tin is associated with metals (titanium, niobium, tantalum, indium, tungsten, iron, manganese, mercury). Knowledge of mineral chemistry and trace-element distribution is essential for: the understanding of ore formation, the exploration phase, the feasibility of ore treatment, and disposal/treatment of tailings after the exploitation phase. However, the availability of analytical methods make these characterisations difficult. We present a multitechnical approach to chemical and structural data that includes scanning electron microscopy (SEM)-based imaging and microanalysis techniques such as: secondary and backscattered electrons, cathodoluminescence (CL), electron probe microanalyser (EPMA), electron backscattered diffraction (EBSD) and confocal Raman-imaging integrated in a SEM (RISE). The presented results show the complementarity of the used analytical techniques. SEM, CL, EBSD, EPMA provide information from the interaction of an electron beam with minerals, leading to atomistic information about their composition, whereas RISE, Raman spectroscopy and imaging completes the studies with information about molecular vibrations, which are sensitive to structural modifications of the minerals. The correlation of Raman bands with the presence/absence of Nb, Ta, Fe (heterovalent substitution) and Ti (homovalent substitution) is established at a submicrometric scale. Combination of the different techniques makes it possible to establish a direct link between chemical and crystallographic data of cassiterite.

The Poopó Polymetallic Epithermal Deposit, Bolivia: Mineralogy, Genetic Constraints, and Distribution of Critical Elements

“…The most noticeable germanium contents were consistently obtained by means of EPMA in rhodostannite (up to 0.21 wt.% Ge) and franckeite (up to 0.16 wt.% Ge), and this element was also quantified in bismuthinite, terrywallaceite, jamesonite, stannite, treasurite, and in unidentified minerals (Table S1). Other strategic elements, such as tantalum, were also analysed in cassiterite, with contents averaging 0.2 wt.% Ta (Table S1), which are comparable to those in other occurrences in the world with soundly determined magmatic origins [34][35][36][37].…”

Tracing fluid saturation during pegmatite differentiation by studying the fluid inclusion evolution and multiphase cassiterite mineralisation of the Gatumba pegmatite dyke system (NW Rwanda)

“…In addition, Ti can substitute isomorphically in cassiterite but spectroscopic identification is not straightforward. However, the intensity of the B2G band is low compared to the AN band when Nb and Ta contents are low and Ti is high (Wille et al, 2018; Fig. 5).…”

LA–ICP–MS U–Pb Dating, Elemental Mapping and In Situ Trace Element Analyses of Cassiterites from the Gejiu Tin Polymetallic Deposit, SW China: Constraints on the Timing of Mineralization and Precipitation Environment

“…The distribution of Nb, Ta, and Ti, revealed by elemental mapping (Figure 6), correlates with the regular oscillatory zoning pattern displayed by CL images. Dark luminescing domains of these cassiterite grains often showed relatively high Sb, Fe, W, Ga, and U, and low Nb and Ta [8,44]. In this study, we discuss skarn (KF-05), and massive sulfide samples (LC-01) in detail as examples.…”