A saga dos descendentes de rodínia na construção de Gondwana

Abstract

All proposed reconstructions for the Rodinia supercontinent published during the last decade use to present a series of problems, of both fundaments (so including some of conceptual nature) and real geologic character. Besides a greater investment in the geological research as a whole, it seems to be necessary to give more attention to the already published articles and look to be acquainted with the regional geology of the countries of the third world. For the particular case of South America there are data enough to point out that the agglutination and the latter fission of Rodinia were rather long and diachronous tectonic processes, from a place to another. The singularity of Rodinia (if it have really existed) as a supercontinet was episodic, a short-living stage. With some good level of confidence, it is possible to state that some of the processes of agglutination (from ~1,5 up to 0,96 Ga) and fission (1,0 – 0,8-0,63 Ga) could coexist and compete for some time intervals, from a province to another.The number of blocks generated during the fission of Rodinia was large and diverse in terms of magnitude, crustal nature, thermal ages, as well as tectonic and rheological behavior during the agglutination of Gondwana, in Neoproterozoic times (up to the Ordovician, in Western Gondwana). Nevertheless, in all reconstrutions of Rodinia already published, only the three largest blocks have been considered, namely the Amazonico, S. Francisco-Congo and Rio de la Plata blocks, what is very far from the geological reality. This paper attempts to discriminate all descendant blocks of Rodinia and their roles and levels of crustal reworking during the construction/agglutination of Gondwana. A second step was to draw a preliminary comparative table, with all possible gradations, since the almost undisturbed large blocks (e.g. Amazonico) up to the small and entirely restructured blocks. There are some particular cases of strong reworking, where the discrimination of the previous blocks was only achieved with the progress of isotopic investigation.