Alpine crustal shear zones and pre-Alpine basement terranes in the Romanian Carpathians and Apuseni Mountains

Abstract

The Carpathian orocline formed by complex suturing of small continental fragments to the East European (and Moesian) plate. Remnants of continental fragments belong to three pre-Alpine lithotectonic assemblages: a greenstone-granite association and two gneissic assem blages. During Alpine collision, pieces of crust were repeatedly fragmented and welded to accommodate heterogeneous strain along the irregular East European plate boundary. Shallow structural levels of Alpine tectonic discontinuities in which the locus of most intense strain migrated over time are now exposed as wide retrograde greenschist grade belts. Repeated, mainly transpressive deformation resulted in early ductile fabrics being overprinted by local brittle shear strain. Igneous intrusion accompanied different phases of tectonic activity. The age of shearing initiation is probably late Paleozoic, and the configuration of the zones and their Alpine internal structures are consistent with the geometry of the Carpathian arc.