“Transmission Electron Microscopy applied to nano mineralogical studies, an innovative approach”

Abigail Jiménez-Franco1,2,3, Josep Roqué-Rosell1,2, José María González Jiménez4, Sandra Baurier-Aymat5, Joaquín A. Proenza1,2, Fernando Gervilla4, Fernando Nieto4, Joan Mendoza6, Trifon Trifonov7, Joaquim Porillo-Serra8.
1. Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, 08028, Barcelona (Spain)
2. Insitut de Nanociència i Nanotecnologia, IN2UB Facultat de Química, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona (Spain)
3. Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, 04510, Cd. de México (Mexico)
4. Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, 18002, Granada, (Spain)
5. Mineral Exploration Research Centre MERC, Harquail School of Earth Sciences, Goodman School of Mines, Laurentian University, 935 Ramsey Lake Rd., Sudbury, , ON, P3E 2C6, (Canada)
6. NanoMEGAS, Boulevard Edmond Machtens 79, Brussels B-1080, Belgium
7. Microscòpia Electrònica de Transmissió Aplicada als Materials, Centres Cientifics i Tecnològics, Universitat de Barcelona, Solé i Sabarís, 1-3, 08028 Barcelona (Spain)
8. Barcelona Research Center in Multiscale Science and Engineering, Universitat Politècnica de Catalunya, Campus Diagonal Besòs – EEBE, Eduard Maristany 10-14, 08930, Barcelona (Spain)

The combined electron microscopy techniques of SEM-EPMA-FIB-TEM-PED offer a new approach to solve unanswered questions in the mineralogy and ore deposits scientific fields. 
For the first time, this approach allowed to characterize sub-micron crystals, with a very low purity and high structural complexity. We applied preparation and characterization of Roqué-Rosell et al. (2018). First, electro-transparent lamellas of ~ 80 mm thick were extracted applying a FIB milling at the Barcelona Research Center in Multiscale Science and Engineering. Then, the lamella TEM characterization is performed. TEM provides chemical and structural information by means of Energy Dispersive Spectroscopy (EDS), High-Magnification (HM), High Resolution (HR), and High Angle-Annular Dark Field (HAADF) imaging, Electron Diffraction (ED) and Fast Fourier Transform (FFT). Especially on complex mineral associations, Precession Electron Diffraction (PED) provided advantageous results compared to conventional ED, such as improved correlation index, reliability for phase identification and plotting orientation maps. This approach opens a new field in the characterization to minerals otherwise considered “too small to study”. Implying certain paradigm changes on the metallogenesis of elements and noble metals with high technological value. Also, new fields of discussion are opened, both in supergenic processes and high-temperature magmatic systems. i.e. the transport of these metals could not take place as dissolved cations in the silicate melts, but as nanoparticles and aggregates. This could revolutionize the classical concepts of mineral forming and growth such as nucleation, partition coefficients, solid solution, exsolution, etc.

Transmission Electron Microscopy applied to nano mineralogical studies, an innovative approach

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