Early Paleozoic accretionary orogens along the Western Gondwana margin

Abstract Early Paleozoic accretionary orogens dominated the Western Gondwana margin and were characterized by nearly continuous subduction associated with crustal extension back-arc basin development. The southwestern is represented Famatinian Pampean basement realms exposed in South America, both related to protracted evolution of Terra Australis Orogen, whereas northwestern mainly recorded Cadomian domains Europe adjacent regions. However, no clear relationships between these regions so far established. Based on a compilation reevaluation geological, paleomagnetic, petrological, geochronological isotopic evidence, this contribution focuses crustal-scale tectonic geodynamic processes occurring orogens, aiming at disentangling their common evolution. Data show that high-temperature/low-pressure metamorphism relatively high geothermal gradients, resulting from development extended/hyperextended margins bulk transtensional deformation. In sense, retreating-mode margin, though short-lived pulses compression/transpression also occurred. existence retreating zones favoured mantle-derived magmatism mixing young (meta)sedimentary sources thin continental crust. Crustal reworking previous forearc sequences due trenchward arc migration thus took place through assimilation anatexis arc/back-arc Therefore, locus growth Gondwana, intimately major flare-up events, such as those Famatian arcs. Slab roll back, probably decreasing convergence rates plate velocities after assembly, was key factor for orogen-scale processes. Coupled synchronous oblique dextral deformation, slab back might trigger toroidal mantle flow, accounting transtension, extension/transtension large-scale anticlockwise rotation mainland.