Pre-Mesozoic basement of Tvarditsa Stara Planina Mountain, Central South Bulgaria: U-Pb geochronology and regional implication

Abstract

The easternmost coherent tract of the pre-Mesozoic basement of the Carpatho-Balkanide belt is exposed in Tvarditsa Stara Planina Mountain. Two metamorphic units – the Lazovo and Shivachevo complexes as well as the Tvarditsa pluton were distinguished, as their ages are still not well constrained. Here, we present U-Pb (ID-TIMS) data for the Shivachevo complex and the Tvarditsa pluton, putting this information in the regional context of the late Variscan geodynamic evolution of the region.

Lower Paleozoic low-grade metamorphic units from the Central Balkan Zone, Bulgaria: tectonic relationships, framework and geodynamic significance

“…The Shivachevo orthogneisses were correlated with the similarly deformed and metamorphosed in medium-to high-grade greenschist facies Carboniferous (zircon U-Pb age of 313.1±4.6 Ma, Antonov et al, 2010b) Ribaritsa granitoids from the Central Balkan Zone (Fig. 2; Dörr et al, 2021). This correlation suggests that, although metamorphosed at a higher degree than the other pre-Permian units of the Balkan Zone, the Lazovo Complex most probably is part of this lithotectonic unit and not of the high-grade basement of the Sredna Gora Zone (Dörr et al, 2021).…”

“…2; Dörr et al, 2021). This correlation suggests that, although metamorphosed at a higher degree than the other pre-Permian units of the Balkan Zone, the Lazovo Complex most probably is part of this lithotectonic unit and not of the high-grade basement of the Sredna Gora Zone (Dörr et al, 2021).…”

“…A protolith zircon U-Pb age of ~600 Ma is obtained from orthogneisses in the eastern part of the complex (Statelova et al, 2011). The Lazovo Complex is juxtaposed along a ductile shear zone with the Shivachevo orthogneisses, which were recently dated at 319-315 Ma (Dörr et al, 2021). The Shivachevo orthogneisses were correlated with the similarly deformed and metamorphosed in medium-to high-grade greenschist facies Carboniferous (zircon U-Pb age of 313.1±4.6 Ma, Antonov et al, 2010b) Ribaritsa granitoids from the Central Balkan Zone (Fig.…”