Critmag

Home » Research » Facilities » Electron microscopy

Electron microscopy

Microanalysis of natural and experimental samples is conducted in the Microbeam Laboratories at the School of Earth Sciences at the University of Bristol.

The laboratory operates a Hitachi S-3500N scanning electron microscope (SEM) for high resolution imaging of geological and biological samples (click here for a more detailed technical specification). In CRITMAG’s work, the SEM is used to acquire images of petrological thin sections and crystals, and is usually conducted in back-scatter mode (BSE) where pixel brightness is proportional to atomic mass of the elements in the field of view. These images are typically taken in preparation for further microanalysis by other techniques; however, the SEM is a proven powerful tool in its own right for textural analysis and element mapping.

Grenada lava BSE

Back scattered electron (BSE) image of a lava from Grenada, Lesser Antilles. The higher the atomic mass, the brighter the object appears. In this sample it reveals compositional zoning within olivine phenocrysts, with Mg-rich (darker) cores and Fe-rich quench rims. Photo is 1 mm across.

 

The Microbeam Laboratories also employ two electron microanalysers (EPMA): a Cameca SX100, which was installed in 2003; and a JEOL JXA8530F Hyperprobe with a Field Emission Gun (FEG) electron source. Both microprobes are equipped with 5 wavelength dispersive spectrometers and 1 energy dispersive spectrometer, and are able to non-destructively analyse the chemical composition of geologic samples.

The FEG-EPMA was purchased in 2012 as part of the CRITMAG grant, and its superior spatial resolution facilitates quantative analysis on nanometre scale. The associated research output is at the forefront of the development of microanalysis and its application to volcanic rocks, particularly diffusion chronometry.

Read more about the CRITMAG FEG-EPMA