This discovery provides an answer to the long-debated question about the origin of these structures in the Earth’s mantle and may be important for understanding similar phenomena on other planets.

The existence of areas of low shear rates in the Earth’s lower mantle has led to various hypotheses regarding their origin.

While some scientists believe these areas are remnants of the early Earth’s material differentiation, others associate them with global tectonics, suggesting that they are clusters of submerged oceanic plates.

The third hypothesis is that these areas ruins of protoplanet Theiacollided with the Earth shortly after its formation. 4.5 billion years ago. This theory is consistent with the geochemical similarities between oceanic island basalts and lunar marine basalts. However, it requires compliance with some physical and chemical conditions.

What scientists discovered

Seismographic studies have revealed the existence of elongated structures in the Earth’s lower mantle, known as large regions of low shear rates. These structures, which can be thousands of kilometers long and up to a thousand kilometers vertically, are characterized by the slower propagation of transverse seismic waves compared to the surrounding mantle.

Although LLSVPs were initially thought to be associated with upward ascent of heated mantle material, subsequent studies showed that they have different boundaries and increased density, leading to questions about their origin and chemical composition.

great simulation

To test the hypothesis that Theia remnants in the Earth’s lower mantle could explain the presence of LLSVP, a team led by Qian Yuan of Arizona State University performed numerical simulations of the impact of the impact.

These simulations used refined equations of state and included empirical constraints on the properties of forsterite, a mineral found in ultramafic igneous rocks. Models show that the early Earth had 90% of its current mass and Theia had 12% of that mass, assuming an impact angle of about 45 degrees.

The models also accounted for changes in Theia’s mantle density based on different iron (II) oxide (FeO) concentrations, ranging from 13 to 17 percent. In all but the minimum density and size values, these molten fragments formed elongated LLSVP-like clusters due to slow mantle convection. Shear seismic wave velocities calculated in these model formations are consistent with observational data and show a 1 to 5 percent reduction relative to the surrounding mantle.

The estimated mass of Theia remnants in LLSVP-like regions was between 1.4 and 2.6 percent of the mass of the Earth. While the study suggests that modern LLSVPs may be a combination of these remnants and fragments of submerged oceanic crust, it also shows that Theia’s material was not completely mixed with other components. Isotope anomalies found in oceanic island basalts derived from the lower mantle support this claim.

The researchers also suggest that similar structures may exist in the mantles of other planets, since large-scale collisions are common in the young solar system.

The results of the research make a significant contribution to our understanding of Earth’s geological history and may have broader implications for planetary science. More research and research is needed to confirm and expand these exciting discoveries.