Neoproterozoic to Early Cambrian history of an active plate margin in the Tepla-Barrandian unit -: a correlation of U-Pb isotopic-dilution-TIMS ages (Bohemia, Czech Republic)

The Tepla-Barrandian unit (TBU) of the Bohemian Massif shared a common geological history throughout the Neoproterozoic and Cambrian with the Avalonian-Cadomian terranes. The Neoproterozoic evolution of an active plate margin in the Tepla-Barrandian is similar to Avalonian rocks in Newfoundland, whereas the Cambrian transtension and related calc-alkaline plutons are reminiscent of the Cadomian Ossa-Morena Zone and the Armorican Massif in western Europe. The Neoproterozoic evolution of the Tepla-Barrandian unit fits well with that of the Lausitz area (Saxothuringian unit), but is significantly distinct from the history of the Moravo-Silesian unit. The oldest volcanic activity in the Bohemian Massif is dated at 609+17/-19 Ma (U-Pb upper intercept). Subduction-related volcanic rocks have been dated from 585 +/- 7 to 568 +/- 3 Ma (lower intercept, rhyolite boulders), which pre-dates the age of sedimentation of the Cadomian flysch (Stechovice Group). Accretion, uplift and erosion of the volcanic arc is documented by the Neoproterozoic Dobris conglomerate of the upper part of the flysch. The intrusion age of 541+7/-8 Ma from the Zgorzelec granodiorite is interpreted as a minimum age of the Neoproterozoic sequence. The Neoproterozoic crust was tilted and subsequently early Cambrian intrusions dated at 522 +/- 2 Ma (Tesovice granite), 524 +/- 3 Ma (Vsepadly granodiorite), 523 +/- 3 Ma (Smrzovice tonalite), 523 +/- 1 Ma (Smrzovice gabbro) and 524 +/- 0.8 Ma (Orlovice gabbro) were emplaced into transtensive shear zones, (C) 2002 Elsevier Science B.V. All rights reserved.