Scientific publications

The Early Mesoproterozoic (1370 Ma BP) age of picrite-picrobasalt volcanism and the associated metamorphism in the riftogenic Ishimbinsko-Tatarskaya suture zone (paleorift) in the southwest of the Siberian Craton is substantiated. Petrogeochemical typification of metavolcanogenic-sedimentary complexes is carried out to establish their protoliths and correlation. First data on Rb-Sr and Rb-Sr и 147Sm-143Nd ID-TIMS systematics of late Precambrian metavolcanogenic rocks in the northern part of the Rybinsk-Panimba volcanic belt in the central part of the North Yenisei Range are presented. According to the petrogeochemical composition, the protoliths of the metavolcanites correspond to picrobasalts and basalts, less often to picrites. As the volcanogenic sedimentary strata in different areas occur on a single marker horizon of carbonaceous shales, we can correlate the age of the volcanogenic Panimba sequence with the Korda suite, considering these formations at the stratolevel of the Early Mesoproterozoic. Geothermobarometry and analysis of the features of regional metamorphism of volcanogenic-sedimentary rocks in the reference areas show a heterogeneous nature of the PT conditions of transformation of the original rocks: 4.8–4.9 kbar/527–549 °C – metatuffites of picrobasalts; 5.0–5.8 kbar/543–612 °C – metabasites; 3.5–4.6 kbar/522–636 °C – metapelites. According to the metamorphic zoning pattern, the progressive metamorphism of the studied rocks belongs to the relatively shallow LP/HT andalusite-sillimanite Idaho type (Buchan type of zoning). Its PT conditions correspond to a transition from the greenschist facies to the boundary between the epidoteamphibolite and amphibolite facies. In terms of the time of manifestation (1056–996 Ma), the metamorphism is close to the Grenville tectonic epoch. The established Precambrian age of picrite-picrobasalt volcanism in the Yenisei Range correlates with the time of manifestation of trondhjemites of the Nemtikhinsky complex and with the reference Mashak plume magmatism in the Southern Urals, which were manifested in a geodynamic setting of continental crust stretching during the breakup of the Nuna supercontinent.