Shear zone evolution and timing of deformation in the Neoproterozoic transpressional Dom Feliciano Belt, Uruguay

Abstract

New structural, microstructural and geochronological (U-Pb LA-ICP-MS, Ar/Ar, K-Ar, Rb-Sr) data were obtained for the Dom Feliciano Belt in Uruguay. The main phase of crustal shortening, metamorphism and associated exhumation is recorded between 630 and 600 Ma. This stage is related to the collision of the Río de la Plata and Congo cratons at ca. 630 Ma, which also involved crustal reworking of minor crustal blocks such as the Nico Pérez Terrane and voluminous post-collisional magmatism. Subsequent orogen-parallel sinistral shearing gave rise to further deformation up to ca. 584 Ma and resulted from the onset of the convergence of the Kalahari Craton and the Río de la Plata-Congo cratons. Sinistral shear zones underwent progressive strain localization and retrograde conditions of deformation during crustal exhumation. Dextral ENE-striking shear zones were subsequently active at ca. 550 Ma, coeval with further sinistral shearing along N- to NNE-striking shear zones. The tectonothermal evolution of the Dom Feliciano Belt thus recorded the collision of the Río de la Plata and Congo cratons, which comprised one of the first amalgamated nuclei of Gondwana, and the subsequent incorporation of the Kalahari Craton into Western Gondwana.