SEM and EPMA Analyses of Metallic Inclusions in Diamonds – Probing the Earth’s Deep Mantle

The Earth’s core is made up of a solid inner portion, encircled by a liquid metallic region [Fig. 1]. Surrounding this is a thick mantle made up of silicates and minor amounts of metal (perhaps reaching 1 wt%), and the outermost layer is the crust, made up of silicates (Figure 1). The mantle is not homogeneous – there are distinct regions of differing mineralogy and composition [2]. Understanding these different regions can inform our ideas of mantle evolution; in particular the carbon cycle in the deep earth, and our knowledge of the redox state (availability of oxygen) within the mantle [3]. Accessing the mantle directly is impossible: our Earth has a radius of ~6400km, and the deepest hole that has been dug to date is the 12km deep Kola Superdeep Borehole in the Kola Peninsula, Russia, which is still within the crust. If we want to learn about the conditions in the deep Earth, then we rely on samples that were created at great depths, and then brought to the surface through geological activity. One of these materials is diamond.