The olivine’s purity, as well as some of the other minerals that were inclusions in the precious rock, indicate a far deeper origin than usual for a diamond, between what’s called the transition zone and the lower mantle zone—420 kilometres to 660 kilometres beneath earth’s surface. It also shows that the environment between these zones has an extremely variable oxygen content.
“To make this extreme composition [of olivine] and the overall mineral assemblage that we’ve got, the only way of doing that is to have a very deeply subducted oceanic plate or slab that goes down into the mantle, so you’re essentially pushing material from the surface of the earth into the depths of the earth,” Graham Pearson, study co-author and director of the Diamond Exploration and Research Training School at the University of Alberta, said in a media statement.
“You get huge gradients in oxygen activity when you do that, and these big…
