By Brendan

Unlike many of our regular contributors I rarely get to venture into the field, thus a large part of my project is spent looking at and analysing rocks sourced from the Earth’s mantle, particularly xenoliths (Greek: foreign rock), which are fragments of rock that are transported by magma (molten rock) from depth to the surface. In my case, by kimberlite magmas from depths between 100-150 km beneath the Kaapvaal craton of South Africa bring xenoliths of peridotite, the most common rock in the mantle to the surface. Therefore most of the images I obtain are taken using various analytical machines and are generally of very small parts of a rock.

From these rocks I then examine thin sections (30-60 µm thick sliver of rock on a glass slide) using petrographic microscopy, followed by scanning electron microscopy and then if things are interesting I will map the distribution of different elements using an electron microprobe, which creates some stunning coloured maps. The main mineral I examine is garnet though there is also spinel, clinopyroxene, orthopyroxene, olivine and phlogopite present in the samples.

Most of the images below were obtained using the Cameca SX100 electron microprobe at RSES.