Diamonds and eclogites of the Jericho kimberlite (Northern Canada)

We studied diamonds and barren and diamondiferous eclogite xenoliths from the Jericho kimberlite (Northern Slave craton). The majority of the diamonds are non-resorbed octahedral crystals, with moderately aggregated N (IaB < 50%, N < 300 ppm) and delta C-13 = -5 to -41aEuro degrees. The diamonds belong to eclogitic (90% of the studied samples), websteritic (7%) and peridotitic (3%) assemblages. The Jericho diamonds differ from the majority of eclogitic diamonds worldwide in magnesian compositions of associated minerals and extremely light C isotopic compositions (delta C-13 = -24 to -41aEuro degrees). We propose that metasomatism triggered by H2O fluids may have been involved in the diamond formation. Multiple episodes of the metasomatism and associated melt extraction of various ages are evident in Jericho eclogite xenoliths where primary garnet and clinopyroxene have been recrystallized to more magnesian minerals with higher contents of some incompatible trace elements and to hydrous secondary phases. The model is supported by the general similarity of mineral compositions in diamondiferous eclogites to those in diamond inclusions and to secondary magnesian garnet and clinopyroxene in recrystallized barren eclogites. The ultimate products of the metasomatism could be websteritic diamond assemblages sourced from magnesian eclogites.