In the collected and studied diamonds from deposits in South Africa, China, Zaire and Sierra Leone, scientists from the University of Nevada (USA) discovered microscopic inclusions of ice of a very rare cubic form. Such ice is called ice-VII. This finding can lead to a reassessment of our understanding of the amount of water hidden in the bowels of the Earth, commented the researchers in the article published in the journal Science.
Scientists note that almost all the ice we are dealing with in ordinary life, for example, from the same refrigerator, is presented in the form of ice-Ih, which has a hexagonal crystal lattice. In general, science knows several dozen other phases of ice, which can be formed under various exotic conditions. Among them is ice-VII, which has a cubic crystal lattice. As a rule, it is found in outer space, but on Earth it was obtained only under laboratory conditions, at extremely high temperatures and pressures.
Nevertheless, a team of miners from the University of Nevada, led by Oliver Zauner, discovered the first natural samples of ice-VII. Scientists believe that the formation of these crystals occurred at depths of 610-800 kilometers, where, as previously thought, there is no water presence. Thus, its presence there can only be explained by the fact that water inclusions could fall deeper beneath the surface, and the increasing temperature and pressure eventually led to the formation of ice-VII.
This region is located on the transitional boundary between the upper and lower mantle of the Earth, and also slightly deeper than it. While it is difficult to say how much water there can be contained, however, its very presence will force geologists to reconsider the energy balance of the mantle and the processes developing in its rocks.