U–Pb-(SHRIMP-II)-age of zircon from granites of Bolshoy Tyuters Island (Gulf of Finland, Russia) and the problem of the Ediacaran thermal event in the region

New data on the U–Pb age (SHRIMP-II) and trace element composition (SIMS) of zircons from granites of Bolshoy Tyuters Island (Outer Islands of the Gulf of Finland) are presented. The upper intersection of the discordia (1825±11 Ma) is taken as the age of crystallization of granites cutting through secondary quartzites, and thereby determines their youngest age. Subconcordant zircons located in the upper part of the discordia has growth oscillatory zoning and geochemical characteristics of zircons of magmatic origin. The age of the lower intersection of discordia and concordia is about 570 Ma, supported by the independent generation of zircons, represented by black in the CL domains and rims in magmatic zircons, which are characterized by increased contents of non-formula elements (light REE, Ca, P, Ti, Nb, etc. ), up to anomalous values. The most probable interpretation of the age of the lower intersection of discordia and concordia can be considered the Timan (Ediacaran) or Finnmark (Early Caledonian) thermal activation of the Fennoscandian Shield, previously established based on zircons from gneisses of the Kola series.