From Jan. 22nd to Jan. 27th 2023 a joint group from ETH Zürich and University of Zürich held the 15th winter school on light- and electron-microscopy. Awarded with a mobility grant from the IRTG, PhD candidate Niklas Wehmann was able to participate in a one-week intensive training to study the state of the art 2D and 3D electron imaging techniques. The program consisted of daily theoretical and practical units.
From the initial choosing of what sample to analyze, through the entire (complex) preparation for the various techniques, the imaging itself and lastly (3D) processing, the course covered the entire process of obtaining high quality 2D/3D image data.
With networks built and tool kits enhanced, Niklas is now eagerly looking forward to applying the new knowledge to his research within the CRC 1211. With the studied techniques he is now able to investigate the intricacies of mineralogical nanostructures even deeper, revealing some clues of how large landscapes are shaped.
The teaching staff included member of both universities as well as from the industry, while participants flew in from all of Europe or even further away.
Author: Niklas Wehmann
Fig 1: Vacuum chamber of a combined focused-ion-beam & scanning-electron-microscope (FIB-SEM). Photo: Nathalie Thor; ScopeM
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Fig 2: Micrograph of a sample of a liver organoid. FIB is used to “dig” trenches around area of interest. Front face is milled by the FIB and scanned by SEM. Photo: ScopeM
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The field work started in the North of "Cerro Coloso" (figure 1), at a hill in the Coast Cordillera of Antofagasta. IRTG fellowship holder Camila Riffo Contreras went on a fieldtrip to collect sample material for project D03 with two other geology students from the Universidad Católica del Norte.
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Figure 1: North of “Cerro Coloso” with view to the South, showing the hill in the Coast Cordillera, where first samples were taken. Photo: Camila Riffo Contreras
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In Cerro Coloso, the sampling team took soil sample profiles at 3 different points in 4 different soil horizons, which can be described as: a surficial crust, a coarse surface, a nodule level and a white hard level with volcanic clasts. From this sampling site, Camila and the students had a beautiful view to the coast of Antofagasta from the top of the hill.
On the second day of field work, the sampling crew visited the Gypsum Mine at the "Península de Mejillones", a mine with beautiful crystals of gypsum. They took samples from all profiles at 4 different points, where they recognised 9 horizons containing 3 different gypsum forms: powdery gypsum, coarse gypsum and crystallized gypsum. In some horizons the coarse gypsum had an orange colour because of oxidation processes.
On the last day of field work, Camila and the students sampled at 3 different sampling locations at the Central Depression of North of Chile.
First sample side was located at the east side of "Posada Rosario" (figure 2), where 4 different profiles were sampled: 2 profiles were samples in old "Calicheras" profiles, where five horizons are outcropping: a surficial crust, a coarse surface, a poorly compacted level with volcanic clasts, a thenardite level and a compacted level with volcanic clasts.
The other 2 profiles were located at little hills (figure 3), where four horizons could be recognised: a surficial crust, a coarse surface, a thenardite level and a powdery level.
One sample point was in a Cinerite Horizon, where the team sampled ash from two different horizons. The last sampling point was at the east side of "Yungay", where the team sampled two different profiles from old "Calicheras", where 5 different horizons are outcropping: a surficial crust, a coarse level with andesitic clasts, a powdery sand layer, a powdery level with small crystals (sugar like) and hard halite.
Overall the team took 76 samples for the project D03, enjoying the beautiful landscape of the dessert and the sunlight. Samples were taken to investigate the distribution of salts in the Atacama Desert and the oxygen-isotope-composition from nitrates.
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Figure 2: Soil profile from the old “Calicheras” at the east side of “Posada Rosario” showing 5 horizons: a surficial crust, a coarse surface, a poorly compacted level with volcanic clasts, a thenardite level (the whitest level) and a compacted level with volcanic clasts at the bottom. Photo: Camila Riffo Contreras
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Figure 3: East side of “Posada Rosario” with view to the North. The little hills show a thenardite level (whitest area) in the soil profile. Photo: Camila Riffo Contreras
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