Petrogenetic significance of minor elements in olivines from diamonds and peridotite xenoliths from kimberlites of Yakutia

Olivines were analyzed for major and minor elements with a JEOL JXA 8200 electron microprobe at the Max-Planck Institute of Chemistry, Mainz. Special efforts were made to obtain high precision and accuracy in electron microprobe analyses, especially, for Ti, Al, Ni, Co, Ca, Mn and Cr. These elements were analyzed by using long counting time and high beam current yielding detection limits of around 10-15 ppm and errors of 20-30 ppm (2 standard errors). Minor element abundance of the overwhelming majority of studied forsteritic (Fo) olivines with Fo [100 Mg/(Mg + Fe)] between 91 and 94 varies within the following ranges in wt.% (NiO 0.310-0.420; CaO 0.005-0.045; MnO 0.070-0.131; Cr2O3 0.012-0.117; CoO 0.008-0.022; Al2O3 0.007- 0.039; TiO2 0.005-0.042). It is concluded that all examined olivines share similar compositional features and are formed at high pressures. A significant positive correlation of Fe and Mn was observed as well as a trend to positive correlation of Cr and Al for a number of samples due to a possible dependence on T values and Cr/Al in bulk peridotites and a trend to positive correlation of Ca and Al due to the effect of temperature.