Geoscience at the nanometre scale: Review of analytical transmission electron microscopy applications

Abstract

This paper describes applications of analytical Transmission Electron Microscopy (TEM) in the geosciences. The topics include: 1) sulphide-mineral oxidation; 2) trace-metal attenuation by secondary Mn oxides; 3) silicate weathering; 4) transition-metal valence in minerals; and 5) secondary Hg minerals in stream sediments. The main advantage of the analytical TEM is the ability to obtain images, chemical information, and electron diffraction patterns at the nanometre scale. With such high spatial resolution, it is possible to observe physical and chemical features in samples that cannot be resolved with most other techniques. This information can lead to significant improvement in our understanding of the system under investigation. Sample preparation techniques that are used in each study are also described in this paper. The preparation of samples for TEM analysis can be challenging because of the heterogeneity commonly encountered in geological materials, the fragility of some geological samples (e.g., low-temperature minerals), and the need to maintain spatial relationships present in the samples. The sample preparation techniques presented are specific to the needs of the study and the appropriateness of these methods is demonstrated by the high quality analytical TEM data that are obtained.