Most current geochemists work on the assumption that the composition of the bulk silicate Earth (crust and mantle – predominately silicate bearing rocks) should be same as the composition of the chondritic meteorites, which are some of the oldest bodies in our solar system. However a paper published yesterday in Nature by two geochemists at RSES – Ian Campbell and Hugh O’Neill challenges this assumption.
They highlight some of the key variations between the Earth and the chondrites such as the ratio of two isotopes of neodymium (142Nd/144Nd) as well as concentrations of some volatile elements which current theories attempt explain using a ‘hidden reservoir’ of material near the core/mantle boundary. Campbell describes this as one of excuses made to keep the chondritic hypothesis (ABC). Although more work is needed to determine the original composition of the Earth this work does have the potential to change the fundamental thinking behind current silicate earth geochemistry.