Geological Applications of Electron Energy-Loss Spectroscopy

Abstract EELS with a TEM is an established spectroscopic technique that is used to provide both qualitative and quantitative chemical information. Analysis of EELS spectral shapes provides information on the coordination, oxidation state, and spin states of atoms in minerals. Despite the availability of parallel EELS detectors for almost fifteen years, geological applications are relatively rare, mainly because of the high level of expertise required by the operator in both acquiring and analyzing the data. For example, core-loss edges can be difficult to see on the background and elemental quantification is not yet routine. The goal of this review is to discuss the uses and interpretations of the EELS spectra of a range of minerals. We will focus on the interpretation of the electron-loss near-edge structures (ELNES) of the core-loss edges and concentrate primarily on: a) determination of the oxidation state of transition elements and other metals, and b) identification of local anion and cation coordinations. In addition, we will explore the potential of ELNES as a bonding probe.