ИСТИНА

Trace elements can significantly affect the properties and phase equilibria of phases under the conditions of the transition zone and lower mantle, providing evidence for geochemical, petrological and geophysical processes in these areas of the Earth. We have found that in the hydrous system sodium preferably incorporates in ferropericlase. In addition, sodium content in ferropericlase increases with temperature. Aluminum content increases with increasing Ca content in calcium perovskite. For the first time at high temperatures and pressures, a phase of the Na2MgSiO4 composition was synthesized, and structure refinement was performed using single-crystal X-ray diffraction. It is shown that this compound, like many other intrinsic phases of sodium, can crystallize as proper phases only under the conditions of strong enrichment of mantle substrate in sodium (e.g., due to deep subduction of crustal material into the mantle and crust-mantle interaction upon low-degrees of partial melting)