Unserpentinized harzburgites of the Voikaro-Synyinsky massif of the Polar Urals as the initial source of chromium for the formation of deposits

The composition and age of unserpentinized harzburgites, which are found in the Voikaro-Synyinsky massif in the form of budins and relict bodies in the fields of olivine-antigorite rocks development, have been studied. The structure, compositions of rocks and minerals, as well as the distribution of rare-earth elements and Sm-Nd absolute dating (≈2330 million years) allow us to consider these unserpentinized harzburgites as fragments of the mantle and the earliest formations among the ultramafic Voikaro-Synyinsky massif. The silicates of these harzburgites are characterized by increased chromium content, which in subsequent different processes turns into chromium spinelide. Based on the data obtained, the resources of chromium mobilized during the transformation of primary ultramafics were evaluated.