An official website of the United States government
Abstract We propose that the mantle lithospheric density and crustal thickness are correlated in such a way as to produce a flat Tibetan Plateau. We observe that the mantle lithosphere is relatively uniform beneath the Himalaya and southern and central Tibet, despite a near doubling of crustal thickness relative to India. Farther north, cratonic mantle lithosphere disappears over large regions of north-central Tibet, giving rise to large lateral variations in uppermost mantle Vs anomalies (>12%) that are uncorrelated with changes in surface elevation but are closely related to changes in crustal thickness. This decoupling of surface topography from spatial variations in upper mantle seismic velocity, and assumed buoyancy, implies that Tibetan topography is controlled by a crust-mantle interaction that is able to maintain its near constant elevation. This crust-mantle interaction is likely driven by gravitational potential energy with a very weak crust. Magmatism, with ages of ca. 20 Ma to Present, spatially correlated with this region with no sub-Moho mantle lithosphere implies destabilization of mantle lithosphere in northern Tibet. Cratonic Indian underthrusting for the past 25 m.y. has also not led to significant topography in the plateau through time. The magmatism may have helped weaken the crust, allowing it to respond to changes in uppermost mantle buoyancy, resulting in a flat plateau.
more »
« less
This content will become publicly available on February 7, 2026
Periodic instability and restoration of cratonic lithosphere
The longevity of cratons usually implies that the entire cratonic lithosphere remained unchanged over billions of years, which is traditionally attributed to their intrinsically buoyant and strong lithospheric roots. By reviewing relevant studies and recent observational constraints, we show that the present cratonic roots are notably denser than the ambient mantle, with the compositional buoyancy offsetting only one-fifth of the negative thermal buoyancy. In addition, the presence of a weak mid-lithospheric discontinuity could decouple the upper and lower lithosphere upon perturbation, allowing delamination of the lower portion, while most of the delaminated lithosphere would eventually relaminate to the base of the lithosphere after sufficient warming inside the convective mantle. This process generates enduring (>100 Myr) and prominent (>1 km) surface uplifts within continents, a mechanism more compatible with data, especially those reflecting lithospheric deformation, than the model of all continents climbing up a steady region of dynamic uplift. Subsequent lithospheric cooling gradually draws the surface down to below sea level, where the lithospheric mantle density reaches a maximum upon formation of the next supercontinent. We argue that such cratonic deformation has happened repeatedly over supercontinent cycles since the Neoproterozoic and has largely shaped the properties of the present cratonic lithosphere. A few new research directions are also suggested.
more »
« less
- Award ID(s):
- 2319445
- PAR ID:
- 10594759
- Publisher / Repository:
- Chinese Academy of Sciences
- Date Published:
- Journal Name:
- National Science Review
- Volume:
- 12
- Issue:
- 3
- ISSN:
- 2095-5138
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Tectonic plate convergence is accommodated across the continental lithosphere via discrete lithospheric subduction or distributed shortening and thickening. These end-member deformation modes control intra-plate mountain building, but their selection mechanism remains unclear. The variable composition of the continental crust and lithospheric mantle, which impacts its density and rheology, can be inferred by the distribution of magnetic-indicated crustal iron. Here we demonstrate that vertically coherent pure-shear shortening dominated the active Tian Shan orogen, central Asia, based on high-resolution aeromagnetic imaging and geophysical-geodetic observations. Integrating these findings with thermomechanical collisional models reveals that the mode of intracontinental deformation depends on contrasts in lower crust composition and mantle lithosphere depletion between the converging continents and central orogenic region. Distributed shortening prevails when the converging continents have a more iron-enriched mafic crust and iron-depleted mantle lithosphere when compared to the intervening orogenic region. Conversely, continental subduction occurs without such lithospheric contrasts. This result explains how the Tian Shan orogen formed via distributed lithospheric thickening without continental subduction or underthrusting. Our interpretations imply that iron distribution in the crust correlates with lithospheric compositional, density, and rheological structure, which impacts the preservation and destruction of Earth’s continents, including long-lived cratons, during intracontinental orogeny.more » « less
-
The relative significance of various geodynamic mechanisms that drive supercontinent breakup is unclear. A previous analysis of extensional stress during supercontinent breakup demonstrated the importance of the plume‐push force relative to the dragging force of subduction retreat. Here, we extend the analysis to basal traction (shear stress) and cross‐lithosphere integrations of both extensional and shear stresses, aiming to understand more clearly the relevant importance of these mechanisms in supercontinent breakup. More importantly, we evaluate the effect of preexisting orogens (mobile belts) in the lithosphere on supercontinent breakup process. Our analysis suggests that a homogeneous supercontinent has extensional stress of 20–50 MPa in its interior (<40° from the central point). When orogens are introduced, the extensional stress in the continents focuses on the top 80‐km of the lithosphere with an average magnitude of ~160 MPa, whereas at the margin of the supercontinent the extensional stress is 5–50 MPa. In both homogeneous and orogeny‐embedded cases, the subsupercontinent mantle upwellings act as the controlling factor on the normal stress field in the supercontinent interior. Compared with the extensional stress, shear stress at the bottom of the supercontinent is 1–2 order of magnitude smaller (0–5 MPa). In our two end‐member models, the breakup of a supercontinent with orogens can be achieved after the first extensional stress surge, whereas for a hypothetical supercontinent without orogens it starts with more diffused local thinning of the continental lithospheric before the breakup, suggesting that weak orogens play a critical role in the dispersal of supercontinents.more » « less
-
Abstract The relative significance of various geodynamic mechanisms that drive supercontinent breakup is unclear. A previous analysis of extensional stress during supercontinent breakup demonstrated the importance of the plume‐push force relative to the dragging force of subduction retreat. Here, we extend the analysis to basal traction (shear stress) and cross‐lithosphere integrations of both extensional and shear stresses, aiming to understand more clearly the relevant importance of these mechanisms in supercontinent breakup. More importantly, we evaluate the effect of preexisting orogens (mobile belts) in the lithosphere on supercontinent breakup process. Our analysis suggests that a homogeneous supercontinent has extensional stress of 20–50 MPa in its interior (<40° from the central point). When orogens are introduced, the extensional stress in the continents focuses on the top 80‐km of the lithosphere with an average magnitude of ~160 MPa, whereas at the margin of the supercontinent the extensional stress is 5–50 MPa. In both homogeneous and orogeny‐embedded cases, the subsupercontinent mantle upwellings act as the controlling factor on the normal stress field in the supercontinent interior. Compared with the extensional stress, shear stress at the bottom of the supercontinent is 1–2 order of magnitude smaller (0–5 MPa). In our two end‐member models, the breakup of a supercontinent with orogens can be achieved after the first extensional stress surge, whereas for a hypothetical supercontinent without orogens it starts with more diffused local thinning of the continental lithospheric before the breakup, suggesting that weak orogens play a critical role in the dispersal of supercontinents.more » « less
-
Deformation-resistant cratons comprise >60% of the continental landmass on Earth. Because they were formed mostly in the Archean to Mesoproterozoic, it remains unclear if cratonization was a process unique to early Earth. We address this question by presenting an integrated geological-geophysical data set from the Tarim region of central Asia. This data set shows that the Tarim region was a deformable domain from the Proterozoic to early Paleozoic, but deformation ceased after the emplacement of a Permian plume despite the fact that deformation continued to the north and south due to the closure of the Paleo-Asian and Tethyan Oceans. We interpret this spatiotemporal correlation to indicate plume-driven welding of the earlier deformable continents and the formation of Tarim’s stable cratonic lithosphere. Our work highlights the Phanerozoic plume-driven cratonization process and implies that mantle plumes may have significantly contributed to the development of cratons on early Earth.more » « less
