Micro-CT Scanning Rock Samples
Using a Micro-CT scanner to investigate the inner structure of rocks
One of the biggest challenges geologists face is being unable to see understand rocks with non-destructive methodologies. Cutting rocks open can often destroy important features, may result in the rock being cut in places with no interesting sites, and sample preparation is long and laborious. We can use X-Ray CT scanning as an alternative, providing a three-dimensional image of the inside of a rock without the need for sample preparation (besides perhaps cutting it down to fit into the machine!). X-Ray CT scanning is a relatively fast, non-destructive method which can distinguish between mineral phases in a rock, and provide in clearer detail where a rock might host it's most exciting features!
The Rock
The rock sample we decided to CT scan is a meteorite from North West Africa. Prior to CT scanning, a section of the meteorite was prepared for analysis by SEM-EDS on our
Zeiss Sigma 300 LV FE SEM
. This was investigative, as the mineralogy of the rock was unknown, but is not a necessary step prior to CT scanning. We learned from this that there would be enough contrast between mineral phases for our CT machine to pick up changes in the attenuation (interaction of minerals with X-Rays) between minerals. Metallic phases (those with iron or sulfur in them) show up particularly well, because they are far denser than the host silicate minerals they reside in. A small piece of the meteorite (2-3 cm in diameter) was attached to a copper stub with Blu Tack and placed into the chamber of the SkyScan 1174.
X-Ray Micro-CT Scan
PEMC has a Bruker SkyScan 1174 X-Ray Micro-CT. For this particular scan, small camera pixels were used (35.54 μm). Rotation was completed at 0.5 steps, with a frame averaging over every 5 frames to enhance smoothness and remove artefacts. The scan was completed in 360°, as the rock is homogeneous and therefore requires a full scan around the entire sample. The scan took 7 hours, at 50 kV (with fluctuations in X-Ray between 48 kV and 50 kV).
As the rock is imaged in its entirety, it can be spliced together to visualize the inside of the rock in high detail. A video of the rock can be viewed below.
