Differences and similarities of lithosphere deformation during flat-slab subduction and plume underplating

Abstract:

Intuitively, upper plate responses during flat-slab subduction and plume-lithosphere interaction should be drastically different due to the contrasting properties of cold strong slabs and hot weak plumes. Here we revisit these intraplate processes since the Mesozoic within several continents.

Using global geodynamic models with data assimilation, we show that both western North America and eastern Asia experienced widespread flat-slab subduction during the Late Cretaceous. The former is consistent with the much-studied Laramide flat slab, but the latter represents a previously unrecognized phase of flat subduction. Combining these model results with geological and geophysical data, we demonstrate that continental deformation above the flat slab is most severe within the lower lithosphere where much of the mass is remove by the advancing slab. The entire region above the flat slab experiences intraplate deformation, with the strongest deformation occurring along the front of the flat slab, where extreme lithospheric shortening lead to intraplate orogeny, corresponding to the Rocky Mountain in North America and Xing’an-Taihang-Xuefeng Mountains in East Asia.

In another study (Hu et al., Nature Geoscience, 2018), we also looked at lithosphere deformation of the western Gondwana region during plume underplating. Instead of local thinning and volcanism above the individual hotspots as traditionally envisioned, we found that the lower lithosphere within a broad region above the plumes was remobilized and deformed, similar to that occurred during underplating of a flat slab. Another similarity is that both geodynamic processes caused extensive lower lithosphere removal. The delaminated lithosphere material due to plume-lithosphere interaction is thought to be preserved in the upper mantle below South Atlantic, and that removed by the two flat slabs is predicted to be below central-eastern U.S. and central-eastern Asia, respectively.