V.G. Kolokol'tsev, S.A. Sergeev (Karpinsky Institute)

CHUPLEGA ORE OCCURRENCE OF TITANIUM PLACERS IN THE NORTH OF THE RUSSIAN PLATE (ARKHANGELSK ARCHED UPLIFT)

In the north of the East European Platform, placer deposits of titanium minerals are known only within the Timan fold-block uplifts separating the Pechora and Russian plates. The only occurrence of titanium-bearing placers in the north of the Russian Plate, the Chuplega ore occurrence, was discovered in the core of a borehole drilled 80 km east of the city of Arkhangelsk in the contour of the cognominal arched uplift. Titanium-bearing sandstones in the Upper Vendian terrigenous sequence, penetrated at a depth of 171.4–71.5 m, contain ilmenite and its transformation products: leucoxene, rutile, anatase, brookite. TiO2 concentrations in them vary from 1.32 to 6.1%. The article presents the geological, lithological, mineralogical, and geochemical characteristics of the ore occurrence and the results of the U-Pb isotope study of detrital zircons obtained for the first time. The datings of zircon from the Chuplega placer are very similar to those from the Timan deposits (giant Yarega oilleucoxene and large Pizhma ilmenite-leucoxene).
The Chuplega ore occurrence is a direct indication of the presence of commercial titaniumbearing placers in the depths of the northern part of the Russian Plate. They can occur at depths (to 200 m) accessible for open-pit mining.
Keywords: Vendian, ore occurrence, ilmenite, direct signs of placers, Yarega deposit, Pizhma deposit, U-Pb zircon studies.