The 2.31 Ga mafic dykes in the Karelian Craton, eastern Fennoscandian shield: U-Pb age, source characteristics and implications for continental break-up processes

摘要

Major- and trace-element geochemistry, Sm-Nd isotopic and U-Pb geochronological (ID TIMS, baddeleyite) data are presented for Paleoproterozoic mafic dykes in the Karelian Craton, eastern Fennoscandian shield. Mafic dyke swarms recognized in the Lake Upper Kuito area in the Western Karelian terrane of the Karelian Craton include (i) NE-trending ca. 2450 Ma gabbronorite dykes, (ii) NW-trending ca. 2310 Ma dolerite dykes, and (iii) NNW-trending ca. 2130 Ma continental MORB-type tholeiitic dykes. Each swarm belongs to a distinct intraplate igneous event and indicates specific mantle melting and extensional processes.