A mechanism for low‐extent melts at the lithosphere‐asthenosphere boundary

摘要: Recent studies have imaged sharp vertical drops in shear wave velocity at the lithosphere-asthenosphere boundary (LAB). In some regions, magnitude of negative gradient LAB is too large to be explained by changes temperature alone. This study demonstrates that small amounts partial melt shallow asthenosphere are a viable model for this seismic boundary. particular, we examine melting upper edge thick cratonic lithosphere, using example eastern North America where has been observed. Finite element modeling asthenospheric flow an abrupt lateral decrease lithosphere thickness indicates geometry, together with plate motions, produces edge-driven convection and upwelling continental margin. A key component work comparison locations extents produced different models depression peridotite solidus varying H2O content. addition, develop simplified parameterization H2O-undersaturated constant degree saturation nominally anhydrous minerals. The patterns mantle our numerical various parameterizations predict less than 0.1 wt % 2.8 (0.01–3.3 vol %) depths between 102 126 km potential 1350°C 150 ppm H2O, or 91 maximum 200 450 H2O. If ≤1340°C contains 3 GPa, no will occur. process generating produce other convective occurs although it dependent on temperature, composition, Because may heterogeneous composition content, onset below fluctuate time space, as drop LAB.