Russian researchers from the V. I. Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences have proven that the Earth's lower mantle has a heterogeneous composition and structure. Until recently, scientists believed that, starting from a depth of 660 kilometers, the Earth's mantle is a homogeneous mass of minerals. However, the latest research has revealed a completely different picture.
In the course of studying deep diamonds from the Juina area in Brazil, specialists analyzed one of the main minerals of the lower mantle — calcium silicate (CaSiO3). It turned out that this mineral exists in two different forms:
- Davemaoite with a cubic crystal structure is formed in the upper parts of the lower mantle.
- Breiite with a less perfect triclinic structure is formed in a smaller transition zone.
It turned out that the minerals differ significantly in composition, especially in the content of rare earth elements — even the isotopic characteristics of lower mantle diamonds turned out to be highly variable. This means that diamonds that are deep underground may have different properties. For example, they may differ in composition and other characteristics, even if they look similar.
According to Felix Kaminsky, chief researcher at the E. M. Galimov Laboratory of Carbon Geochemistry of the GEOKHI RAS, areas with different compositions may be either remnants of the primary substance of the deep Earth, or areas of mantle convection currents, or associated with transformed areas of the Earth's crust, sinking all the way to the Earth's core in the process of subduction of oceanic plates.
Further research into these areas will help scientists better understand how magmatic provinces are formed on the surface of our planet. The work was supported by the Ministry of Education and Science of Russia, and the results are published in the authoritative journal «Geochemistry International».
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