The Cerro Durazno, Brealito, and Cobres granitoid plutons belong to the eastern Ordovician magmatic belt of northwest Argentina and are associated with a network of NW‐ and N‐striking ductile shear zones. A structural analysis of these plutons and their metamorphic host rocks was conducted to elucidate mid‐ to upper‐crustal magmatism and tectonism at the western margin of Gondwana. Pluton emplacement took place at 480–455 Ma, toward the end of a ca. 75‐Ma‐long episode of regional deformation and high‐temperature metamorphism. The Cerro Durazno and Brealito plutons were probably emplaced as NE‐SW‐striking, vertical magma sheets that coalesced into large magma bodies under overall E‐W shortening that generated SW‐dipping metamorphic foliations at a later stage of pluton formation. These fabrics were superimposed to the magmatic structures in the granite plutons and to the high‐grade metamorphic structures of the host rocks. At the northern pluton margins, ductile high‐strain zones, notably the Agua Rosada Shear Zone north of the Cerro Durazno pluton, further localized ascent of granitoid magma. Similarly, emplacement of the Brealito and Cobres plutons is genetically related to prominent shear zones. Geometry and metamorphic character of the shear zone network in the eastern Ordovician magmatic belt point to orogen‐parallel extension and transverse shortening of the belt under variable metamorphic conditions. The width as well as protracted deformation, high‐temperature metamorphism, anatexis, and granitoid magmatism of the magmatic belt are key characteristics of a hot, wide orogen that evolved during the lower Paleozoic at the western margin of Gondwana. Remarkable geotectonic similarities with respect to the modern Andes point to comparable plate‐tectonic conditions at the lower Paleozoic and the Cenozoic convergent plate margins.