Lithospheric layering in the North American craton
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Summary
This summary is machine-generated.Stable continental cratons feature two distinct lithospheric layers, not one. This finding resolves discrepancies between seismic and geochemical data, revealing a mid-lithospheric boundary.
Area Of Science
- Geophysics
- Geochemistry
- Tectonics
Background
- Cratons are ancient, stable continental crustal areas, with their formation and preservation over billions of years being a significant geological debate.
- Seismic receiver function studies have identified a shallow structural boundary beneath cratons, inconsistent with the traditional lithosphere-asthenosphere boundary (LAB).
Purpose Of The Study
- To investigate the structure of the North American continent's lithosphere using seismic anisotropy.
- To reconcile conflicting geophysical and geochemical data regarding cratonic lithosphere structure.
Main Methods
- Analysis of seismic-wave azimuthal anisotropy changes with depth.
- Comparison of seismic data with geochemical inferences from xenolith thermo-barometric analysis.
- Integration of seismological, geochemical, and geodynamical data.
Main Results
- Evidence for two distinct lithospheric layers in the North American continent, identified by azimuthal anisotropy.
- The upper layer's thickness correlates with a highly depleted chemical layer.
- A relatively flat lithosphere-asthenosphere boundary (180-240 km depth) exists, likely a thermal root around the depleted layer.
Conclusions
- The detected shallow seismic boundary likely represents a mid-lithospheric boundary, not the LAB.
- The findings integrate diverse datasets, providing a unified model for North American cratonic lithosphere.
- This study clarifies the complex structure and evolution of ancient continental lithosphere.