Oriolo, Sebastián

English

The Sarandí del Yí Shear Zone (Uruguay) is a crustal-scale structure that separates the Río de la Plata Craton from the Nico Pérez Terrane and Dom Feliciano Belt. Nevertheless, its evolution is poorly constrained, even though it represents a key structural feature of Western Gondwana. A multidisciplinary study was thus carried out, in order to assess the tectonic evolution of the Sarandí del Yí Shear Zone and adjacent blocks and the crustal affinity of the latter. Likewise, new and available data were integrated to provide a unified tectonic model for the history of amalgamation of Gondwana and the evolution of major mobile belts during the Neoproterozoic. 
Geological, geochronological and isotopic data indicate that the Nico Pérez Terrane originated mostly from Archean episodic crustal growth and underwent dominantly crustal reworking during several Proterozoic events, whereas the Piedra Alta Terrane is made up of juvenile Paleoproterozoic continental crust. Hence, the Nico Pérez Terrane was allochthonous to the Río de la Plata Craton. In contrast, it shows an African crustal affinity and probably derived from the southwestern margin of the Congo Craton. Similarities of Archean and Proterozoic events recorded in the Nico Pérez Terrane basement and the overlying metasedimentary cover of the southwestern Dom Feliciano Belt further support an African derivation.
The onset of the deformation along the Sarandí del Yí Shear Zone is recorded at 630-625 Ma, giving rise to dextral shearing, and is coeval with the onset of deformation, metamorphism and exhumation of the Dom Feliciano Belt. This is related to the collision of the Río de la Plata and Congo Craton and the consequent juxtaposition of the Nico Pérez Terrane to the Río de la Plata Craton margin. Subsequent post-collisional exhumation, deformation and magmatism are ubiquitously recorded in the Dom Feliciano Belt up to 600 Ma. Sinistral shearing at ca. 600-580 Ma took place along the Sarandí del Yí Shear Zone as well as along NNE-striking shear zones of the Dom Feliciano Belt, and resulted from the onset of the Kalahari convergence with the already amalgamated Río de la Plata and Congo cratons. The input of Kalahari-derived sediments is restricted to the late Ediacaran southeastern post-collisional sequences of the Dom Feliciano Belt, which further indicates that the Congo-Río de la Plata amalgamation predates the accretion of the Kalahari Craton. 
	As in the case of the Sarandí del Yí Shear Zone, collisional events up to 600 Ma along crustal-scale shear zones can be further traced to the north along the Transbrasiliano-Kandi Lineament, which gave rise to the birth of Western Gondwana. The late stages of Rodinia break-up associated with the opening of the Iapetus Ocean between Laurentia, Baltica and Amazonas occurred contemporaneously and were succeeded by collisional events at 580-550 Ma of the East African/Antartic Orogen. The latter gave rise to the amalgamation of Eastern and Western Gondwana and predated the incorporation of the Kalahari Craton into Gondwana during the late Ediacaran-early Cambrian. 
Hence, the assembly of Gondwana comprised a protracted history of amalgamation of crustal blocks between ca. 630 and 530 Ma. Likewise, the existence of the Pannotia supercontinent can be ruled out, as the final configuration of Gondwana was attained during the early Cambrian and took place after rifting between Laurentia and Amazonas

Georg-August-University Göttingen

Tectonothermal evolution of the Sarandí del Yí Shear Zone and adjacent blocks (Uruguay): Implications for the assembly of Western Gondwana

https://ediss.uni-goettingen.de/bitstream/11858/00-1735-0000-0028-87EF-D/1/Oriolo%202016%20Dissertation.pdf

Tectonothermal evolution of the Sarandí del Yí Shear Zone and adjacent blocks (Uruguay): Implications for the assembly of Western Gondwana

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Georg-August-University Göttingen