Geologists have shed light on the destruction of one of Earth's oldest cratons.

The stable internal sections of the continental crust are known as cratons. These are the "cores" of all current continents. It was previously believed that nothing had changed in these areas for billions of years; however, a recent international team of geologists has discovered signs of degradation, deformation, and thinning in the North China craton.

2024-11-04 11:45:28https://naked-science.ru/article/geology/razrushenie-kratona

No changes have been recorded within the cratons: they are characterized by a lack of volcanic and seismic activity, faults, or rock formation. Moreover, throughout Earth's geological history, these massive, deep blocks have assembled into supercontinents and "drifted" across the surface while remaining stable and cold.

However, one of the oldest foundations of the continental crust has been subjected to destruction. This was reported by an international research team in an article published in the journal Nature Geoscience, after studying signs of lithosphere thinning and significant deformation of the North China Craton since the beginning of the Mesozoic era (i.e., over the last 200 million years).

The team, led by Shaofeng Liu (Shaofeng Liu) from the China University of Geosciences, analyzed data on mantle and lithosphere movement using computer modeling, which they then combined with a large array of geological, geochemical, and geophysical data. This allowed the researchers to understand how processes deep within the Earth affect its surface structures.

To visually illustrate the results, the team created a video demonstrating the dynamics of the model and its consequences. Researchers also explained the mechanism through which subduction (the sinking of one lithospheric plate beneath another) of the flat oceanic plate Izanagi and its subsequent retreat could lead to the thinning and deformation of the craton.

The team divided the deformation process of the North China Craton into two main phases that occurred over several tens of millions of years. The first led to the subduction of Izanagi beneath the Eurasian Plate, but instead of advancing deeper into the mantle, it aligned and began moving parallel to the continental plate. This resulted in the shortening and thickening of the lithosphere and the subsequent formation of the Taihangshan mountain range in northeastern China.

Then Izanagi began to retreat (the second phase), moving deeper in the opposite direction. This caused the lithosphere to stretch and subsequently thin by about 26 percent. The process also contributed to the heating and erosion of the craton's base and was accompanied by magmatic activity.

Geologists also reported several episodes of crustal extension that began approximately 136 million years ago but were interrupted by compression during the Late Cretaceous period (around 93-80 million years ago). After this, extension resumed and continues to this day, contributing to the destruction of the craton.

Thus, both phases and the subsequent processes have led to significant changes in the region's topography, which are reflected in sedimentary basins and the formation of new geological structures. The rapid retreat of the Izanagi plate, along with changes occurring at depths of approximately 660 kilometers, played a key role in transforming the North China Craton.

The team noted that their developed model corresponds to the evolution of the surface and the current structure of lithospheric plates. The results also significantly expand scientists' knowledge of Earth's dynamics and have practical implications. Specifically, lithospheric deformation influences the formation of mineral resources and may aid in predicting seismic activity.