Some features in the basement rocks near the eastern coast of Brazil probably can be explained by plate-tectonics concepts. The area studied contains east-west-oriented diabase dikes, intrusive alkalic rocks, and miogeosynclinal sediments in a fault-bounded sedimentary basin now metamorphosed to greenschist facies, all affected by a northwest-southeast-trending shear zone. These features evolved chronologically in the sequence indicated, about 1,160 to 600 m.y. ago. The model devised by Sengör indicates that these features are possibly the product of a Precambrian collision between two continents with irregular margins.