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)

Abstract

Palaeomagnetic and isotope (U-Pb, 40Ar-Ar39) 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 – 60o with respect to stable Europe in the Carboniferous, most probably during the oroclinal bending of the north-eastern segment of the Variscan orogenic belt.