Ultrabasic rocks of ore fields of the Middle Timan: petrogeochemical and geochronological data

Ultrabasic dike formations developed within the Kosyuskoe, Novobobrovskoe and Oktyabrskoe rare-metal-to-rare-earth ore fields, are attributed to alkaline picrites by the petrographic, petrochemical and geochemical characteristics. The rocks contain high amounts of V, Cr, Ni being typical of ultrabasic rocks. The processes of fenitization increase the content of Th, REE, Y, Pb in the rocks and so cause the appearance of ore minerals (monazite, xenotime, phosphates, and Th and Pb sulfides). The age identified by the 40Ar/39Ar method by phlogopite is 598.1±6.2 Ma. This time period is reconstructed for the plume impulse within the Chetlas Kamen of the Middle Timan.