Mineral inclusions in diamonds: associations and chemical distinctions around the 670-km discontinuity

摘要: Three new mineral associations have been discovered within diamonds from the Juina district of Brazil. These include a previously unrecorded Na-Al-(Mg, Fe)SiO3 phase associated with ferropericlase and tetragonal almandine pyrope phase, TAPP. Also reported are an association corundum aluminous-pyroxene olivine composition ferropericlase. The minerals in each often occurred same addition to being recovered individual different combinations. High-pressure experimental data indicate that these formed at depths region ca. 60 km on either side upper-mantle/lower-mantle boundary. Mineral compositions show for regions sampled, deep transition zone lower mantle chemically distinct inhomogeneous. Importantly, shallow mantle, Al is not solely accommodated perovskite-structured (Mg, as some recent studies suggested.