ABSTRACT
Two types of diamondiferous kimberlites were established in Arkhangelsk Kimberlite Province. Type I kimberlites are represented by high diamond-bearing rocks of the V. Grib pipe (Verkhotinskoye field). They are characterized by a presence of the Ti-chromite, Mg-ulvospinel, titanomagnetite, picroilmenite, rutile and perovskite in kimberlite groundmass and picroilmenite, pyrope and Cr-diopside among the indicator minerals of the heavy fraction. Megacrysts of picroilmenite, low chromium clinopyroxene, low chromium Ti-pyrope were distinguished. Xenoliths of the coarse-grained and sheared peridotites and eclogites were established. Octahedral (37%) and polyhedral diamond crystals (O-D type) are widely spread in the V. Grib pipe. Type II kimberlites are represented by diamond-bearing rocks of the Zolotitskoye field (M.V. Lomonosov deposit). Ti-chromites (>70%), Cr-ulvospinel and sphene prevail in the groundmass of these kimberlites, and ilmenite and rutile are absent. Chromite prevails among the indicator minerals of the heavy fraction and picroilmenite is absent, garnet and Cr-diopside are rare. Xenoliths of ilmenite rocks are not found and sheared peridotites are rare. Megacysts are not found. Round dodecahedral diamonds prevail (>60%).
