LASTING MANTLE SCARS LEAD TO PERENNIAL PLATE TECTONICS: DAMAGE STRUCTURES, JELLY SANDWICHES, AND A CRèME BRûLéE

Deep seismic reflection profiles have found numerous sites of mantle lithosphere deformation, which have often been interpreted simply as ancient relict subduction (termed here as "scars"). A reinterpretation of these heterogeneities could allow tectonic processes related to continent-continent collisions (and the absorption of a plate boundary to a plate interior) to be the origin of deep long-lived mantle lithosphere structures. Despite seismological imaging suggesting that inherited mantle lithosphere heterogeneities are ubiquitous, their plate tectonic role is rarely considered. In a suite of thermal-mechanical numerical experiments of the crust and mantle, we reconsider the past, present and future plate tectonic role of long-lived pre-existing deformation, or scarring, within the mantle lithosphere.

Our results show that deep lithospheric anomalies can dominate shallow geological features in activating tectonics in plate interiors – if the strength of the mantle lithosphere is relatively high. We found that structures frozen into the mantle lithosphere through plate tectonic processes can behave as quasi-plate boundaries reactivated under far-field compressional forcing, if a ‘jelly sandwich’ lithospheric strength profile is followed. Conversely, models featuring a ‘crème brûlée’ lithospheric rheology show that crustal processes dominate surface tectonic evolution over deeper mantle lithosphere structures.

Intraplate locations in strong continental interiors (e.g., jelly sandwich rheology) where proto-lithospheric plates have been scarred by earlier suturing, could be regions where latent plate boundaries remain, and where plate tectonics processes are expressed as a ‘perennial’ phenomenon.

We look to build on this numerical study of the mantle lithosphere with a holistic approach alongside the broad earth science community - in particular the fields of geochemisty, structural geology, and tectonics.