The fingerprint of imperial topaz from Ouro Preto region (Minas Gerais state, Brazil) based on cathodoluminescence properties and composition
| Autor: | Isolda de Castro Mendes, Leonardo Martins Graça, Gláucia Nascimento Queiroga, Leonardo Evangelista Lagoeiro, Teodoro Gauzzi |
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| Rok vydání: | 2018 |
| Předmět: |
Materials science
010504 meteorology & atmospheric sciences Scanning electron microscope Analytical chemistry Mineralogy Crystal growth Cathodoluminescence Electron microprobe engineering.material 010502 geochemistry & geophysics 01 natural sciences Topaz chemistry.chemical_compound symbols.namesake chemistry Geochemistry and Petrology symbols engineering Luminescence Raman spectroscopy 0105 earth and related environmental sciences EMPA |
| Zdroj: | Mineralogical Magazine. 82:943-960 |
| ISSN: | 1471-8022 0026-461X |
| DOI: | 10.1180/minmag.2017.081.078 |
| Popis: | A study of the cathodoluminescence (CL) properties of imperial topaz from Ouro Preto region (Minas Gerais state, Brazil) and its relation with trace-element composition was conducted, using scanning electron microscope cathodoluminescence (SEM-CL), optical microscope cathodoluminescence (OM-CL), cathodoluminescence-spectrometry (CL-spectrometry), electron microprobe analysis (EMPA), laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) and Raman spectrometry. Each analytical technique allowed characterization of the imperial topaz fingerprint. SEM-CL panchromatic images show different crystal growth and resorption events in imperial topaz crystals. Colour CL images indicate only blue to violet emissions. The CL-spectra indicate a broad emission band with low intensity peak at ~417 nm and a broad emission band with high intensity and major peaks at 685, 698, 711 and 733 nm. The EMPA indicates high OH content, in which the OH/(OH + F) ratio ranges between 0.35–0.43 (0.72 ≤ OH ≤ 0.86 apfu). High Cu and Zn concentrations (LA-ICP-MS) were measured in the high luminescence areas of SEM-CL images, suggesting both elements as CL-activators in imperial topaz. Raman and CL-spectra indicate high Cr concentrations, corroborated by EMPA and LA-ICP-MS results. The high Cr caused strong luminescence intensities that enabled their superimposition over the OH stretching mode (~3650 cm–1) of topaz in all Raman spectra. Among trace elements, the concentrations of Ti, V, Cr, Mn, Fe, Cu, Zn, Ga and Ge provide the fingerprint of imperial topaz. |
| Databáze: | OpenAIRE |
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