Evidence of lower-mantle slab penetration phases in plate motions

摘要: It is well accepted that subduction of the cold lithosphere a crucial component Earth's plate tectonic style mantle convection. But whether and how subducting plates penetrate into lower subject continuing debate, which has substantial implications for chemical thermal evolution mantle. Here we identify lower-mantle slab penetration events by comparing Cenozoic motions at main zones with predicted fully dynamic models upper-mantle phase subduction, driven solely downgoing density. Whereas older, intrinsically denser, occurs rates consistent model, younger (of ages less than about 60 Myr) often subducts up to two times faster, while trench are very low. We conclude most likely explanation older lithosphere, under significant retreat, tends lie down flat above transition high-viscosity mantle, whereas able drive retreat deforms more readily, buckles thickens. Slab thickening enhances buoyancy (volume density) thereby Stokes sinking velocity, thus facilitating fast penetration. Such an interpretation seismic images distribution subducted material in upper Thus direct expression time-dependent flow between