U-Pb age and Hf isotope compositions of zircons from the north-western region of the Ukrainian shield: mantle melting in response to post-collision extension

Terra Nova, 24, 373379, 2012 Abstract The North-Western region of the Ukrainian shield represents Palaeoproterozoic continental crust formed essentially during two orogenic events at ca. 2.12.05 and 2.01.95 Ga. At 1.81.74 this area was intruded by huge Korosten anorthositemangeritecharnockite granite complex. At least three generations of mafic dykes can be distinguished in the region. We report new U-Pb data obtained for a suite of Ni-enriched dolerite dykes and layered gabbroic intrusions. Our results indicate that the Tomashgorod dyke was formed at 1787.4 +/- 6.4 Ma, the Prutivka intrusion at 1777.0 +/- 4.7 Ma and the Kamenka massif at ca. 1.79 Ga. This time coincides with the collision of the Fennoscandian and Sarmatian segments of the East European craton and it is contemporaneous with the initial stages of evolution of the Korosten complex. Hf isotopic compositions of zircons indicate that these rocks originated due to melting of moderately depleted mantle material.