A mantle-plume trigger for one of Earth's largest Precambrian silicic large igneous provinces in the Amazonian Craton

Abstract

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° 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 ∼2.5°N, 61.2°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.