Two Possible Models Mantle-derived basalt model Crustal melt or mixed magma restite of m-crust melting Remaining initial basaltic crust restites of basaltic crust melting Mantle-derived andesite model boninite restite of m-crust melting Remaining initial basaltic crust high-T peridotite Basaltic Crust High-V Lower crust normal mantle Upper crust Middle crust Low-V low-V mantle Moho
{}