X-ray spectroscopy helped to investigate the diamond crystals collected on the fields in Africa, China, Zaire and Sierra Leone, and to find in them microinclusions ordinary water ice, but in a rare cubic phase of ice VII. The find, which scientists report in an article published by the journal Science, may lead to a reassessment of our ideas about the amount of water hidden in the bowels of the Earth.
It is worth saying that almost all the ice with which we deal in everyday life, presented in the form of ice Ih from a hexagonal crystal lattice. However, there are about a couple dozen other phases of ice that can form when various unusual conditions. Among them, and ice VII a cubic lattice, which is still able to obtain only in the laboratory under extremely high temperatures and pressures.
However in natural diamonds, the mineralogist Oliver Zauner (Oliver Tschauner) and his colleagues managed to detect the first “natural” samples of ice VII, which forms microscopic inclusions. Scientists suggest that the formation of these crystals occurred at depths 610-800 km, where before it generally does not imply the presence of water. This initially liquid inclusions of water had to descend deeper, so that the temperature and pressure increased and led to the formation of ice VII.
This area is located on the border between the upper and lower mantle of the Earth, and deeper of her. While it is difficult to tell how much water is contained here, but its very presence will force geologists to reconsider the energy balance of the mantle and the processes developing it in rocks.