Modifying the Cratonic Lithosphere: The Role of Mantle Plumes Revealed by the Permian Tarim Large Igneous Province

Cratons are ancient continental crust formed primarily in the Archean-Mesoproterozoic ages. Their perceived stability has been challenged over the past decades. Investigations reveal that cratonic lithosphere contains weak layers/zones at various scales and can undergo destabilization, leading to large-scale delamination under specific tectonic perturbations. Mantle plumes represent a key mechanism for such cratonic destruction. The Tarim Craton, amalgamated from Archean crystalline basements in the Neoproterozoic, hosts a Permian large igneous province potentially linked to plume activity, making it a natural laboratory for studying plume-craton interaction. This study systematically compiles geochemical data from Permian magmatic rocks in the Tarim Craton. Focusing on mafic-ultramafic and alkaline rocks with MgO >8 wt%, we employ an experimentally calibrated whole-rock thermobarometer to estimate the pressure-temperature conditions of melt generation, thereby constraining the paleo-lithospheric thickness. Integrating these results with seismic evidence for a mid-lithosphere low-velocity zone (the mid-lithospheric discontinuity, MLD) beneath Tarim, we propose a novel model: By the late Carboniferous, an MLD had developed at ~100 km depth in the craton lithosphere. The initial arrival of a mantle plume at the lithospheric root generated minor kimberlitic and carbonatitic melts. The thick (~200 km) lithosphere initially impeded the plume's ascent until delamination of the root below the MLD occurred. This removal enabled more efficient heating and melting of the upper lithosphere, producing voluminous flood basalts. Subsequent upwelling and melting of the plume itself formed the mafic-ultramafic rocks. Concurrently, interaction between the plume and the metasomatized MLD generated a portion of the alkaline melts. This process induced a local thickening of the MLD to ~130 km, consistent with its present-day depth. Our findings indicate that the mantle plume first thinned and subsequently thickened the cratonic lithosphere, with the MLD playing a crucial role in this evolution. This mechanism of cratonic destruction followed by "healing" may have operated not only in the Paleozoic but also during the Proterozoic, suggesting it could be a vital process for the episodic destabilization of cratons throughout geological time.