The fate of delaminated cratonic lithosphere

Accretion of the cratonic mantle lithosphere via massive regional relamination

“…Similar heterogeneities are found in younger orogenic and oceanic regions, where evidence from geological and geophysical studies shows ancient, depleted peridotites embedded within or beneath younger fertile peridotites ( 13 – 16 ). This provides proof that the embedding of delaminated, exotic, older, and depleted mantle in the growing lithosphere is a relevant component of the evolution of the Earth’s outer shell ( 13 , 14 , 17 , 18 ), potentially contributing to the construction of the continents.…”

“…We therefore designed models with a ΔT p covering the range of mantle T p difference with respect to the present day from 0 to greater than +300 °C ( 31 ). We considered a CLM block, detached from its crust ( 18 , 34 ), and simulated the sinking processes that do not rely on early Earth tectonic regimes ( 35 – 38 ) or different foundering triggers ( 39 , 40 ). We did not address the initial conditions leading to the formation of the CLM ( 5 – 7 , 41 ) but instead tested a range of different CLM masses related to depletion and CLM shape.…”

“…The mantle weakening factor ( f vis = 0.1 to 1.0) was also tested, which reproduced the effect of melt and fluids ( 44 ). This approach followed similar setups in previous works investigating the sinking of foundered lithosphere in the mantle ( 18 , 43 ), where similarly simplified initial shapes were adopted. We designed a reference group with a model setup including a thick (160 km) cratonic block sinking in the dry ambient mantle, with no water- or fluid-related weakening, following previous works ( 18 , 44 ).…”

“…Delamination of the older continental lithospheric mantle is a fundamental process of continental evolution, compatible with different tectonic regimes, resulting in lithospheric thinning and craton destruction and critically defining the nature and evolution of mantle heterogeneities ( 2 , 5 , 12 , 17 , 19 – 22 ). The cycle of mantle heterogeneities is best understood as a large-scale process involving sinking and mixing of variable volumes of CLM, as well as the upwelling of CLM residue ( 18 ), driven by long-lasting chemical buoyancy, and its eventual embedding in the growing lithosphere. The subsequent upwelling of CLM residue and relamination of the new lithosphere may contribute to the characteristic source, age, and compositional heterogeneities of cratons.…”

“…The majority of depleted, cold CLM is compositionally buoyant ( 25 ) but achieves negative buoyancy due to thermal contraction; thus, once decoupled, it founders into the ambient mantle. Once in the ambient mantle, compositional buoyancy may counteract the vanishing thermal negative buoyancy, opposing sinking, allowing the foundered CLM to rise and relaminate the base of the growing lithosphere ( 13 , 17 , 18 ). The complex feedback between mantle flow, heat transfer, viscosities, and thermal and compositional buoyancy provides key constraints on the spatiotemporal evolution of foundered CLM, including its sinking, transportation, stagnation, upwelling, relamination, and deep mixing, relevant to the interpretation of the physical and chemical mantle anomalies at different depths ( 17 , 20 , 26 – 30 ).…”