Co-evolution of Continental Lithosphere and Deep Mantle Dynamics
Introduction: Unveiling the Mysteries of the Continental Lithosphere
The Earth’s continental lithosphere, the foundation of human habitation, harbors numerous unresolved mysteries. Traditional plate tectonics theory suggests that continental drift is driven by oceanic plate movements, with the continental lithosphere passively responding to deep mantle processes primarily at plate boundaries or hotspots. However, recent research challenges this perspective, revealing that the continental lithosphere, especially cratons, is far from static. Many cratons have undergone structural changes, and their dynamic properties—such as density and viscosity—deviate significantly from long-held assumptions. This sets the stage for exploring the co-evolution between the continental lithosphere and deep mantle dynamics.
Advances in Deep Mantle Dynamics Research
1. Mantle Thermal-Chemical Evolution and Convection
The Earth’s long-term evolution involves heat dissipation and chemical transformations within its interior. Geodynamic studies focus on mantle convection driven by temperature and density variations. Seismic tomography has been instrumental in mapping mantle structures, revealing subducting slabs, low-velocity provinces, and other anomalies. These structures help elucidate how mantle convection influences surface topography and lithospheric behavior. For example, dynamic topography—caused by mantle convection—can generate large-scale surface changes, although uncertainties persist in translating seismic velocities to density structures.
2. Oceanic Subduction and Continental Lithosphere Modification
Oceanic subduction is a key process modifying the continental lithosphere. Flat subduction, where oceanic plates slide horizontally beneath continents, can induce extensive continental deformation, as observed in regions like western North America and East Asia. This process not only affects nearby tectonic activities but also influences the structure and stability of cratons. Stagnant slabs in the mantle transition zone can also alter overlying lithosphere through fluid release, leading to magmatism and lithospheric thinning.
3. Mantle Plume-Lithosphere Interactions
Mantle plumes, originating from the core-mantle boundary, interact with the lithosphere, forming hotspots and large igneous provinces. While oceanic hotspots are better understood, interactions with continental lithosphere remain complex. Continental plumes are rarer but can trigger significant lithospheric modifications, such as rifting and volcanic activity. The interplay between mantle plumes and continental lithosphere is crucial for understanding supercontinent cycles and craton evolution.
Continental Lithosphere’s Response and Role in Deep Processes
1. Structure and Properties of Continental Lithosphere
Continental lithosphere, especially ancient cratons, has a complex structure. Unlike short-lived oceanic lithosphere, cratons can be over 2.5 billion years old. Recent studies reveal that cratonic mantle lithosphere has higher density and layered viscosity, with a mid-lithospheric discontinuity (MLD) at 70–100 km depth. This MLD can decouple lithospheric layers, promoting instability and potential delamination. Such properties challenge the traditional view of cratonic stability, indicating active participation in deep processes.
2. Dynamic Responses of Continental Lithosphere
The continental lithosphere responds to deep processes through mechanisms like dynamic topography, lithospheric thinning, and delamination. Delamination—where dense lower lithosphere detaches—can be triggered by processes such as flat subduction or mantle plumes. This not only modifies the lithosphere but also affects surface topography and sedimentation. For example, craton uplift and subsidence cycles, observed globally, can be linked to lithospheric delamination and reattachment, illustrating the co-evolution between the lithosphere and deep mantle.
Scientific Significance of Co-evolution
The recognition of the continental lithosphere’s active role in deep processes transforms our understanding of Earth’s evolution. Traditional plate tectonics emphasized passive continental responses, but now we recognize mutual influence between the lithosphere and mantle. Supercontinent cycles, where lithospheric delamination and reattachment occur, drive long-term geodynamic changes. This co-evolution is critical for explaining phenomena like craton destruction, supercontinent formation, and global climate change, as lithosphere-mantle interactions affect energy and mass exchange.
Conclusion and Future Prospects
The continental lithosphere and deep mantle dynamics are deeply intertwined, co-evolving over supercontinent cycles. Future research should focus on validating the lithosphere’s active participation through observations and models, developing multi-scale thermochemical models, and constructing comprehensive Earth system models. These efforts will deepen our understanding of the complex interactions shaping our planet.
DOI: 10.1360/TB-2023-0867
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