Inclusions in super-deep diamonds: windows on the very deep Earth

Abstract

Diamonds are the deepest terrestrial materials that reach the Earth’s surface after a very long and complex travel through our Planet. In detail, these pure-carbon minerals might be formed at very variable depths in the mantle from about 120–250 km, so-called “lithospheric diamonds” or from about 300–1000 or more km, so-called “super-deep diamonds”. Both lithospheric and super-deep diamonds can transport minerals and/or fluid inclusions within them, which are real “fragments of deep Earth” allowing geologists to better understand how the Earth works at those great depths. Although super-deep diamonds only represent about 6% of the global diamond population, such special objects are extremely intriguing as they form at depths potentially even >1000 km in the mantle, opening new scenarios on what we knew about the interior of the Earth. This is why super-deep diamonds are among the most studied samples in mantle mineralogy. In this review, I will focus on the two most common mineral inclusions in super-deep diamonds, ferropericlase (Mg,Fe)O, and CaSiO3-walstromite, on the recent discovered hydrous ringwoodite Mg2SiO4 within a Brazilian diamond and on a new category of large diamonds, called CLIPPIR.