Is the mantle chemically stratified? Insights from sound velocity modeling and isotope evolution of an early magma ocean

摘要: Abstract The upper mantle is widely accepted to be pyrolitic, but the bulk composition of lower remains highly disputed. Recent modeling shear wave velocity profile has suggested that enriched in bridgmanite, therefore implying a higher Si/Mg than mantle. We improve upon such by taking into account Ca-perovskite and considering distribution Fe between bridgmanite ferropericlase, more appropriate for Al-bearing systems. Using available experimental data, we derive means constrain Fe–Mg partitioning suitable values mantle, apply these calculations. Calculations consider effects minor chemical components as Ca Al suggest velocities can resolve PREM pyrolitic within 1%. also model fractionations 147 Sm– 143 Nd 176 Lu– Hf systems induced crystallizing magma ocean would produce putative Si-enriched comparison calculated Nd/ 144 Hf/ 177 signatures with those terrestrial array shows if ever formed, no longer exists. Both mineralogical calculations geochemical support idea Earth's likely whole need not chemically stratified.