Late Neoproterozoic Island-Arc Volcanic Associations in the Accretion Belt at the Southwestern Margin of the Siberian Craton (Predivinsk Terrane of the Yenisei Ridge)

Based on geological, geochemical, and isotope-geochronological studies, the geodynamic nature of the island-arc magmatic associations of the Predivinsk terrane of the Yenisei Ridge has been established. It is shown that the Predivinsk terrane consists of two blocks, which differ in age and composition of rock associations. The Eastern Block is composed of the following associations: (1) typical island-arc differentiated calc-alkaline basalt–andesite–dacite association dominated by andesites and dacites; (2) bimodal subalkaline metabasalt–trachyrhyolite association, which is enriched in incompatible elements, was formed under extensional conditions, and reflects the evolution of subduction magmatism, and (3) ophiolite fragments consisting of N-MORB metabasalts. The Western Block is composed of geochemically primitive metabasalt–plagiorhyolite and moderately differentiated calc-alkaline metabasalt–basaltic andesite–rhyodacite associations typical of oceanic island arcs. The magmatic associations of the Eastern Block are dated within 650–630 Ma, while volcanic and sedimentary associations of the Western block, within 620–600 Ma. The accretion of the island-arc complexes of the Predivinsk Terrane and their amalgamation to the Siberian margin occurred about 610–600 Ma.