Birth, evolution, and consumption of the Neoproterozoic Adamastor Ocean: New data from the Ribeirão da Folha Ophiolite, Araçuaí Orogen

The geological history and role of the Ribeirão da Folha Ophiolite in the construction of the Araçuaí Orogen were investigated to establish temporal and geochemical constraints for the evolution of the Adamastor Ocean. Through petrological, geochemical, and isotopic (U-Pb, Lu-Hf, and Sm-Nd) analyses, this study presents the newly discovered Granjas do Norte meta-ultramafic body, which serves as a fundamental record of the oceanic lithosphere history of the Macaúbas Basin. New U-Pb zircon ages obtained from a chloritite sample reveal a complete ca. 140 Myr metasomatic and metamorphic chronology for the northern Adamastor Ocean: from the metasomatic record of its opening at 745 ±11 Ma to the fluid-mediated onset of subduction at 661 ±3 Ma, culminating in regional metamorphism at 606 ±3 Ma during advanced subduction-accretion. The juxtaposition of rocks with magmatism from intraplate (OIB) and supra-subduction zone (SSZ) settings in a tectonic mélange with a pervasively deformed mylonitic matrix, combined with the polyphasic evolution of fluids from the subducted plate and the crust, provides robust evidence that subduction was the dominant mechanism for the closure of the Adamastor Ocean. These results provide direct evidence that challenges intracontinental models and contributes to understanding the complete life history of the Adamastor Ocean.