<p>The Grib kimberlite in NW Russia erupted into a poorly defined cratonic region along the White Sea coast. This region is part of the East European (or Baltica) Super-Craton that is comprised of several cratonic nuclei, including the Kola, Karelian and Murmansk. The eastern extent of the Kola-Karelian-Murmansk cratonic regions is uncertain due to a lack of exposed basement crust. We analysed olivine from a suite of 17 peridotite xenoliths from the Grib kimberlite in NW Russia for their Re-Os isotopic compositions and platinum-group elements (PGE) contents. Os isotopic compositions range from unradiogenic (below the present-day ¹⁸⁷Os/¹⁸⁸Os of the primitive upper mantle, i.e., &lt; 0.1296) to values more radiogenic than any estimate of the primitive upper mantle (PUM). We observed no correlation between the amount of melt depletion reflected by olivine Mg# [100 × molar Mg/(Mg + Fe)] and the most unradiogenic Os isotopic composition measured in the inclusions within olivine. Samples with unradiogenic ¹⁸⁷Os/¹⁸⁸Os have similar PGE_N patterns (where the subscript N indicates normalisation to CI chondrite), that are typical for depleted cratonic peridotites, with depletion in Pd_N and Re_N compared to the iridium-group (I)-PGE_N (Os, Ir, Ru). Only one Grib peridotite xenolith has an Archaean T_RD age of 3.27 ± 0.37&#xa0;Ga. The majority of Grib peridotite xenoliths have Proterozoic T_RD ages between 2.5 and 1.2&#xa0;Ga. Three olivines have ¹⁸⁷Os/¹⁸⁸Os between 0.136 and 0.316, more radiogenic than present-day PUM. Geothermobarometry of Grib peridotite xenoliths show that the local lithospheric mantle is between 210 and 240&#xa0;km thick, with diamond stability below 130&#xa0;km. Overall, the majority of mantle lithosphere beneath this portion of the East European (or Baltica) Super-Craton has a minimum age between 2.5 and 1.2&#xa0;Ga suggesting significant lithosphere modification during Proterozoic rifting and subduction/accretion events.</p>