Combined field structural analysis with in situ electron probe microanalysis Th‐U‐Pb monazite dating, petrologic, and microstructural data provides a reconstruction of the pressure‐temperature‐deformation‐time (P‐T‐D‐t) path of the Gondwanide basement of the North Patagonian Cordillera. For samples from the Challhuaco hill, the timing of development of the metamorphic S2 foliation and associated L2 lineation and tight to isoclinal F2 folds is constrained by monazite ages of 299 ± 8 and 302 ± 16 Ma during peak metamorphic conditions of ~ 650 °C and 11 kbar, achieved during prograde metamorphism and progressive deformation. Metamorphism and deformation of metamorphic complexes of the North Patagonian Andes seem to record Late Paleozoic crustal thickening and are coeval with metamorphism of accretionary complexes exposed further west in Chile, suggesting a coupled Late Devonian‐Carboniferous evolution. Instead of the result of continental collision, the Gondwanide orogeny might thus be essentially linked to transpression due to advancing subduction along the proto‐Pacific margin of Gondwana. On the other hand, second generation of monazite ages of 171 ± 9 and 170 ± 7 Ma constrains the timing of low‐grade metamorphism related to kink band and F3 open fold development during Jurassic transtension and emplacement of granitoids. Finally, a Cretaceous overprint, likely resulting from hydrothermal processes, is recorded by monazite ages of 110 ± 10 and 80 ± 20 Ma, which might be coeval with deformation along low‐grade shear zones during the onset of Andean transpression.
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The Gondwana megacontinent was composed of different domains separated by self-lubricated weak lithospheric zones, two of which could have extended into Laurasia. Displacement vectors determined through three consecutive paleomagnetism-constrained paleogeographic reconstructions (Early Pennsylvanian-early Guadalupian, ca. 320-270 Ma; late Guadalupian-Middle Triassic, ca. 260-240 Ma; and Late Triassic-early Late Jurassic, ca. 230-160 Ma) show similar orientations to coeval tectonic stresses along Gondwana. Triggered by slab pull at the northern subduction margin of the Paleotethys Ocean, differential displacements between the Gondwana domains caused localized deformation along their borders, reactivating old weak lithospheric zones (e.g., Ventana fold belt south of Buenos Aries province, Argentina; basins such as Cuvette in central Africa; and Neuquén on the Pacific margin of Gondwana). We propose that the wide extent of these structures was possible due to the transmission of mantle toroidal flow induced by strike-slip movements along these focused self-lubricated weak lithospheric zones, along with the northward drift of Pangea. These processes occurred simultaneously with a major mantle reorganization from a huge cold downwelling to a hot upwelling event caused by thermal energy storage beneath Pangea.
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