Ferropericlase included in diamond: lower or upper mantle origin?

Ferropericlase [(Mg,Fe)O] is a common oxide found as inclusions in diamonds considered to be of lower mantle origin (i.e. from below 660 km depth). Indeed, ferropericlase is often associated with low-Ni enstatite and such enstatite could be the inversion product of MgSiO3 perovskite. Nonetheless, ferropericlase is stable over the entire mantle P-T range and its relative abundance as inclusions in diamonds with respect to possible inverted MgSiO3 is much higher than expected based on high-PT experiments. In order to provide new and stronger evidence of lower mantle origin for ferropericlase inclusions, we are investigating four diamonds from Juina (Brazil). By measuring the residual stress on the inclusions, and combining it with knowledge of the EoS of the diamond and the inclusion, it is possible to determine the isomeke that defines possible minimum P and T of entrapment (Angel et al., 2014). This elastic measurement could thus contribute to resolve the question as to whether ferropericlase inclusions in diamond originate entirely in the lower mantle, whether or not enstatite inclusions are also present.