Résumé
The Amazonian Craton is host to one of Earth's largest Proterozoic silicic large igneous provinces (SLIPs), the Orocaima SLIP (ca. 1.98 Ga). Nevertheless, the mechanism(s) responsible for this large-flux felsic magmatic event and its relationships with regional tectonics and/or mantle processes remain debated. New geochronologic and geochemical results from multiple mafic dike swarms in the Amazonian Craton, namely the Guaniamo, Rio Aro, El Manteco-Supamo, and Goboy swarms, reveal a close temporal, spatial, and geochemical association with the Orocaima SLIP. The radiating arrangement of these swarms spanning 90 degrees of arc, their strongly tholeiitic geochemical affinity, and their short-lived emplacement ca. 1.98 Ga including in regions far from any inferred subducting plate margins all strongly suggest: (1) an intraplate, plume-related origin, and (2) a radiating arrangement defining a plume center located at approximately 2.5 degrees N, 61.2 degrees W, near the SW margin of proto-Amazonia at the time and coinciding with the location of the Takutu graben. Discovery of this previously unrecognized radiating swarm array, herein grouped within a proposed Yanomami large igneous province, and its close spatial and temporal association with the Orocaima SLIP suggests a plume-triggered origin for SLIP development, thus arguing against accretionary models for the origin of the Orocaima silicic magmatic belt.