Palaeomagnetic study of Palaeoproterozoic granitoids from the Voronezh Massif, Russia

A palaeomagnetic investigation has been carried out of rocks from the easte rn part of the Voronezh Massif, which constitutes, together with the Ukrain ian Shield, the Sarmatian segment in the southern part of the East European Craton. The samples were collected in a quarry close to the town of Pavlov sk (50.4 degrees N, 40.1 degrees E), where a syenitic-granitic body intrude s Archaean units. U-Pb (zircon) dating has yielded an age of 2080 Ma for th e intrusion. Two characteristic magnetic components, A and B, were isolated by thermal a nd alternating-field demagnetization. Component A was obtained from granite s and quartz syenites (11 samples) and has a mean direction of D = 229 degr ees, I = 28 degrees, and a pole position at 12 degrees N, 172 degrees E. Th is pole is close to a contemporary mean pole (9 degrees N, 187 degrees E) f or the Ukrainian Shield, which implies that the Voronezh Massif and the Shi eld constituted a single entity at 2.06 Ga. These poles differ from contemp oraneous poles of the Fennoscandian Shield, indicating that the relative po sitions of the two shields were different from their present configuration about 2100 Myr ago. A component B, isolated only in quartz monzonites (five samples), has a mea n direction D = 144 degrees, I = 49 degrees, and a pole position at 4 degre es N, 251 degrees E, which is close to late Sveconorwegian (approximately 9 00 Ma) poles for Baltica. This suggests that the East European Craton was c onsolidated some time between 2080 and 900 Ma. Comparison with other palaeo magnetic data permit us to narrow this time span to 1770-1340 Ma.