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Convective self-compression of cratons and the 1 stabilization of old lithosphere
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  • Jyotirmoy Paul,
  • Clinton P Conrad,
  • Thorsten W Becker,
  • Attreyee Ghosh
Jyotirmoy Paul
Bayerisches Geoinstitut, Universität Bayreuth

Corresponding Author:jyotirmoyp@iisc.ac.in

Author Profile
Clinton P Conrad
Department of Geosciences, Centre for Earth Evolution and Dynamics (CEED), University of Oslo
Thorsten W Becker
Institute for Geophysics, Jackson School of Geosciences, Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Oden Institute for Computational Engineering & Sciences, The University of Texas at Austin
Attreyee Ghosh
Centre for Earth Sciences, Indian Institute of Science

Abstract

Key Points: 13 • Mantle flow leads to inwardly convergent tractions around the edges of cratons, 14 and compressive stresses within. 15 • Convergent tractions result from the downward diversion of mantle flow. 16 • This convective self-compression could help stabilize older lithosphere against con-17 vective erosion. Abstract 19 Despite being exposed to convective stresses for much of the Earth's history, cratonic roots 20 appear capable of resisting mantle shearing. This tectonic stability can be attributed to 21 the neutral density and higher strength of cratons. However, the excess thickness of cra-22 tons and their higher viscosity amplify coupling to underlying mantle flow, which could 23 be destabilizing. To investigate the stresses that a convecting mantle exerts on cratons 24 that are both strong and thick, we developed instantaneous global spherical numerical 25 models that incorporate present-day geoemetry of cratons within active mantle flow. Our 26 results show that mantle flow is diverted downward beneath thick and viscous cratonic 27 roots, giving rise to a ring of elevated and inwardly-convergent tractions along a craton's 28 periphery. These tractions induce regional compressive stress regimes within cratonic in-29 teriors. Such compression could serve to stabilize older continental lithosphere against 30 mantle shearing, thus adding an additional factor that promotes cratonic longevity. 31 Plain Language Summary 32 Cratons are the oldest continental relicts on Earth. Due to plate tectonics and man-33 tle convection, many non-cratonic rocks get recycled. However, cratons have escaped tec-34 tonic recycling, and some have remained stable for more than ∼ 3 billion years. Previ-35 ous studies have shown that cratons' high strength and neutral buoyancy provide them 36 with tectonic stability. Here we show that the deep roots of cratons also help to stabi-37 lize them. This is because mantle flow is deflected downward beneath thick cratonic roots, 38 and this deflection generates a ring of inwardly-directed forces around the edges of the 39 craton. These inward forces compress the craton interior. Such self-induced compressive 40 stresses may further help to stabilize Earth's oldest lithosphere. 41
22 Jan 2023Submitted to ESS Open Archive
24 Jan 2023Published in ESS Open Archive