Inclusions in diamonds are fantastically useful for studying the inaccessible part of the deep Earth. It’s a bit like studying extinct insects in amber. Although we can’t extract DNA and grow dinosaurs, we can extract their chemical compositions and tell where they formed by growing minerals in the lab at extreme conditions.
Mineral inclusions discovered in diamonds prove that surface rocks can be subducted into the deep part of the Earth's mantle. The isotopic composition of the diamonds confirms that recycling of crustal materials, including carbon, extends into the lower mantle. The theory of plate tectonics is at the centre of our understanding of how the Earth works. It has been known for decades that new crust is formed at mid-ocean ridges and that this crust is subducted as plates dive underneath other plates in regions such as the Pacific Ring of Fire and descend into the Earth's mantle. What is not so well known is the fate of these subducted plates. In this week's edition of the journal Science , scientists from the University of Bristol (Professor Michael Walter, Simon Kohn, Galina Bulanova, Mr Christopher Smith), Universidade de Brasilia (Professor Débora Araujo), and the Carnegie Institution of Washington (Dr Eloise Gaillou, Junyue Wang, Andrew Steele, Steven Shirey), show that oceanic crust can make its way right down to the lower mantle (deeper than 660km) and then be transported back to the surface. The samples studied are tiny inclusions of minerals trapped in diamonds from the Juina region of Brazil.
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