U-PB BADDELEYITE AGES FOR THE NOVA LACERDA AND SALTO DO CÉU MAGMATIC INTRAPLATE EVENTS IN THE PALEOPROTEROZOIC JAURU TERRANE: EVIDENCE FOR WIDESPREAD 1.4 GA EXTENSIONAL TECTONICS IN THE SW AMAZONIAN CRATON, AND GLOBAL IMPLICATIONS

High-quality U-Pb (ID-TIMS) baddeleyite ages were obtained for the Salto do Céu mafic sill (1439 Ma) and Nova Lacerda mafic dyke swarm (1387 Ma) located ca. 150 km apart in the 1975-1970 Ma Alto Jauru granite-greenstone terrane (Rio Negro-Juruena tectonic province) - SW portion of the Amazonian Craton. These ages highlight the role of Mesoproterozoic extensional tectonics, likely coeval with the polycyclic evolution of the adjoining Rondonian-San Ignacio province (1.59–1.30 Ga) as part of a growing Amazonia. The latter province was formed through successive amalgamation of magmatic arcs accompanying Mesoproterozoic oceanic closure and involved eventual collision between the allochtonous Paraguá block and the Rio-Negro-Juruena tectonic province. In this dynamic tectonic setting, the mafic magmatism described here is age-equivalent with the Santa Helena batholith and the Pensamiento Granitoid complex, as a reflex from outboard development of the Alto Guaporé collisional belt along the proto-Amazonian continental margin, preceding final docking of the Paraguá block and the Rio Negro-Juruena province. From a global perspective, our data provide new clues as to the longevity of the Columbia (Nuna) supercontinent, supported by previously published paleomagnetic poles from Mesoproterozoic rocks with intraplate affinity in Amazonia and Baltica (SAMBA model).