Integration of elemental and isotope data supports a Neoproterozoic Adamastor Ocean realm
Fabrício de Andrade Caxito, Mônica Heilbron, Cláudio de Morisson Valeriano, Henrique Bruno, Antônio Carlos Pedrosa‐Soares, Fernando F. Alkmim, Farid Chemale, Léo Afrâneo Hartmann, Elton Luiz Dantas, Miguel Ângelo Stipp Basei
Abstract
A robust elemental and isotopic dataset from Neoproterozoic igneous rocks discloses protracted consumption of oceanic lithosphere in the 3,000 km long orogenic system of southeastern South America. Time dependent isotopic variation trends suggest that Tonian-Cryogenian magmatic rocks formed in intra-oceanic supra-subduction settings, followed by Ediacaran magmatic arc building along Andean-type continental margins. Tectonic slices of basic-ultrabasic rocks associated with deep sea and exhalative rocks are interpreted as remnants of obducted oceanic lithosphere. Protracted closure of the oceanic realm resulted in a Himalayas-sized orogenic belt during Ediacaran-Cambrian collision, as recorded by voluminous aluminum-rich syn-collisional granites followed by post-collisional intrusions. The duration and rates of crust forming processes in island arc, continental margins and collisional settings imply that a vast Adamastor oceanic realm was consumed to form western Gondwana.