Convective Self‐Compression of Cratons and the Stabilization of Old Lithosphere. Issue 4 (14th February 2023)

• Record Type: Journal Article
• Authors: Paul, Jyotirmoy; Conrad, Clinton P.; Becker, Thorsten W.; Ghosh, Attreyee
• Is Part Of: Geophysical research letters. Volume 50:Issue 4(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-02-14
• Subjects: craton -- numerical model -- mantle convection -- geodynamics; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL101842
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Despite being exposed to convective stresses for much of the Earth's history, cratonic roots appear capable of resisting mantle shearing. This tectonic stability can be attributed to the neutral density and higher strength of cratons. However, the excess thickness of cratons and their higher viscosity amplify coupling to underlying mantle flow, which could be destabilizing. To investigate the stresses that a convecting mantle exerts on cratons that are both strong and thick, we developed instantaneous global spherical numerical models that incorporate present‐day geoemetry of cratons within active mantle flow. Our results show that mantle flow is diverted downward beneath thick and viscous cratonic roots, giving rise to a ring of elevated and inwardly‐convergent tractions along a craton's periphery. These tractions induce regional compressive stress regimes within cratonic interiors. Such compression could serve to stabilize older continental lithosphere against mantle shearing, thus adding an additional factor that promotes cratonic longevity. Plain Language Summary: Cratons are the oldest continental relicts on Earth. Due to plate tectonics and mantle convection, many non‐cratonic rocks get recycled. However, cratons have escaped tectonic recycling, and some have remained stable for more than ∼3 billion years. Previous studies have shown that cratons' high strength and neutral buoyancy provide them with tectonic stability. Here we show that the deep roots of cratons also help to stabilize them. This is because mantle flow is deflected downward beneath thick cratonic roots, and this deflection generates a ring of inwardly‐directed forces around the edges of the craton. These inward forces compress the craton interior. Such self‐induced compressive stresses may further help to stabilize Earth's oldest lithosphere. Key Points: Mantle flow leads to inwardly convergent tractions around the edges of cratons, and compressive stress within Convergent tractions result from the downward diversion of mantle flow This convective self‐compression could help stabilize older lithosphere against convective erosion