New data on Mesoproterozoic picrite-picrobasalt volcanism (North Yenisei Ridge)

In the northern part of the Rybinsk-Panimbinsk volcanic belt, the first Rb-Sr and ¹⁴⁷Sm-¹⁴³Nd results on early Mesoproterozoic rift picrite- picrobasalt volcanism and metamorphism were obtained. Petrogeochemical data indicate the sedimentary-terrigenous nature of most of the samples of the Mikhailovsky site taken from the section of the Kordinsky formation. The presence of a noticeable admixture of basitic matter in them in the form of tuffs or washed volcanomictic material is confirmed by an increased content of MgO and CaO, reduced REE, Zr, Hf and Nb. The results of geothermobarometry and analysis of the metamorphism features of volcanogenic-sedimentary rocks of the reference sites show the heterogeneous nature of the initial rock transformation conditions: 4.8-4.9 kbar/527-549°C – picrobasalt metatuffites; 5.0–5.8 kbar/543-612°C – metabasites; 3.5-4.6 kbar/522-636°C – metapelites. The established age of riftogenic picrite-picrobasalt volcanism and related somewhat late metamorphism processes in the Precambrian of the central part of the Yenisei Ridge correlates with the time of formation of plagiogranites of the Nemtikhinsky complex and with the reference Mashak plume magmatism in the South. In the Urals, manifested in the geodynamic environment of stretching during the collapse of the supercontinent Nuna.