The compositional peculiarities of microinclusions in diamonds from the Lomonosov deposit (Arkhangelsk province)

The data on the composition of microinclusions in diamonds from the Lomonosov deposit are reported. The studied diamonds include coated (n = 5) and cubic (n = 5) crystals. The determined range of the degree of nitrogen aggregation (4-39 %B1) in diamonds does not support their links with kimberlite magmatism, but their short occurrence in the mantle at higher temperatures is probable as well. The composition of melt/fluid microinclusions in these samples varies from essentially carbonatitic to significantly silicate. It is shown that the content of MgO, CaO, Na2O, Cl and P2O5 decreases with increasing content of silicates and water. Different mechanisms of generation and evolution of diamond-forming media are considered to explain the observed variations.