Detrital Tourmaline from the Riphean Terrigenous Deposits of the Middle Timan: Chemical Composition and Genesis

Data on the chemical composition and a degree of roundness of detrital tourmaline from the Chetlasskaya, Bystrinskaya, Vymskaya, and Kislorucheyskaya groups of Upper Precambrian metaterrigenous rocks of the Middle Timan are presented. Fragments of the studied tourmaline crystals are predominantly homogeneous (without visible concentric and sectorial zoning) and belong to the alkaline group and hydroxy subgroup (dravite and schorl) of the tourmaline supergroup. The similarity in chemical compositions indicates a unified source of fragments of this mineral for all studied Riphean sedimentary rocks within the studied region, and a low degree of roundness, the proximity of the primary source. Comparison of tourmaline with associated detrital zircon made it possible to conclude that metamorphic complexes of the terrains of the Grenvillian–Sveconorwegian orogenic belt were the source of clastic material for the formation of Upper Precambrian metaterrigenous rocks in the Middle Timan.