Y-REE-Rich zircons of the Timan region: Geochemistry and economic significance

Mineralogical-geochemical studies of zircon from the Ichet'yu occurrence revealed unusually high Y and HREE contents (correlative with the P content) in the inner parts and zones of approximately 10% of the grains. They represent the intermediate members of the zircon-xenotime join with a heterovalent scheme of isomorphism Zr4+ + Si4+ -> (Y + HREE)(3+) + P5+. Geochronological and mineralogical-geochemical data suggest that the Middle Timan basement (the most probable source of zircon of the Ichet'yu occurrence) is made up of the Paleoproterozoic rocks and possibly represents a continuation beneath the Mezen syneclise and Middle Timan of the Paleoproterozoic collisional structure, to which the Arkhangelsk diamond province is confined.