Ti-Zr placer mineralization in neoproterozoic (upper riphean) rocks of kildin formation and in contemporary beach sands of Sredny and Rybachy peninsulas, Kola region

Concentration mechanisms of titanium-zirconium placer mineralization in Neoproterozoic terrigenous rocks of Zemlepakhtinskaya Formation, Kildin Group, and in contemporary beach deposits from Sredny Peninsula and Motka Cape from Rybachy Peninsula (Kola region) have been considered in the paper. It has been shown that the rocks of Zemlepakhtinskaya Formation are facially variable. The shallow littoral facies are confined to the western and central parts of Sredny Peninsula, the deeper sublittoral facies are confined to the eastern part of Sredny Peninsula and to Motka Cape of Rybachy Peninsula. It has been established that lenses and beds with titanium-zirconium placer mineralization occur solely in littoral facies. The ore minerals in aleurite-psamite of Zemlepakhtinskaya Formation are represented by leucoxene, rutile and zircon, and in contemporary beach deposits - by ilmenite, rutile and minor zircon. Paleogeographic reconstruction indicates that almost all deposits of Neoproterozoic (Upper Riphean) Kildin Group were accumulated in shallow (littoral and sublittoral) environment during dominant humid climate and intense weathering of source area. Thus, not only deposits of Zemlepakhtinskaya Formation, but also the whole succession of Kildin Group can be regarded perspective for placers' accumulation. The low grade of heavy minerals (mainly Ti and Zr minerals) in contemporary beach deposits from Sredny Peninsula and Motka Cape from Rybachy Peninsula is related to weak weathering of the Baltic Shield during Quaternary and to accumulation of coarse debris in littoral zone, preventing the differentiation of sand by wave action.