Basic problems concerning the composition of the Earth's lower mantle

The last decade has seen the publication of a number of new and highly pertinent studies on the composition of the Earth's lower mantle, leading to a better understanding of the Deep Earth. A series of new lower-mantle minerals were found, having formed under natural conditions and received the following names: bridgmanite, jeffbenite, breyite, and ellinaite. Some other, as yet, unnamed oxides, phosphates, and fluorides were also discovered for the first time. Among the new mineral phases, of particular interest are cubic nitrogen and ice-VII. Their presence demonstrates a significant role of both nitrogen and of water in the Deep Earth. This new data allows for creation of a principal model for the composition of the Earth's lower mantle. By various evidences, it differs greatly to that of the upper mantle composition, and is heterogeneous. •The Earth's lower mantle differs in composition of the upper mantle.•The lower mantle is heterogeneous in its composition.•The lower mantle is a great reservoir of N, H2O, and other volatile elements.•The enstatite-chondrite model is likely for the Earth's origin.