Mid-Ediacaran Bimodal Magmatism And Peri-Baltic Affinity Of The Brunovistulian Terrane Documented By The U-Pb Isotope And Palaeomagnetic Data From The Brno Massif (Central Europe)

Palaeomagnetic and isotope (U-Pb, Ar-40-Ar-39) studies were conducted in the area of the Brno Massif (Central Europe). The basaltic and granitic dykes, so far regarded as Silurian, were sampled in four localities. New U-Pb isotope ages and palaeomagnetic data indicate that the studied magmatic intrusions, most probably of bimodal type, penetrated the Brno Massif in the mid-Ediacaran (ca 575-565 Ma ago). Palaeomagnetic data support the thesis that the Brunovistulian terrane, a larger tectonostratigraphic unit containing the Brno Massif, was incorporated into the peri-Baltic part of the Cadomian orogenic belt and, at least since the mid-Ediacaran, had a common drift history with Baltica. It crossed the polar region of the southern hemisphere between 580 and 560 Ma. The Brno Massif rotated clockwise by 50 - 60 degrees with respect to stable Europe in the Carboniferous, most probably during the oroclinal bending of the north-eastern segment of the Variscan orogenic belt.