Sluggish thermochemical basal mantle structures support their long-lived stability.
Zhidong Shi1,2, Ross N Mitchell1,2, Yang Li3,4
1State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China.
Nature Communications
|November 20, 2024
Summary
Numerical models reveal that large low shear-wave velocity provinces (LLSVPs) in the deep mantle likely formed from thermochemical structures. These ancient, slow-moving features explain geological observations over millions of years.
Area of Science:
- Geophysics
- Earth Sciences
- Mantle Dynamics
Background:
- Large low shear-wave velocity provinces (LLSVPs) are enigmatic, massive structures in Earth's deep mantle.
- Geological evidence suggests LLSVPs have been stable for at least 200 million years.
Purpose of the Study:
- To investigate the origin and long-term stability of LLSVPs.
- To model the formation of basal mantle structures resembling LLSVPs.
Main Methods:
- Numerical modeling of mantle convection incorporating plate-like behavior.
- Parameterization of models to match observed LLSVP characteristics.
Main Results:
- A Pacific-like downwelling girdle successfully generated two antipodal basal mantle structures similar to LLSVPs.
- Modeled thermochemical structures exhibited velocities approximately four times slower than the ambient mantle, consistent with long-term stability.
Conclusions:
- The sluggish, thermochemical nature of modeled basal mantle structures supports their ancient origin and stability.
- This provides a potential mechanism linking geological observations across hundreds of millions of years to modern LLSVPs.
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