The Rio Apa Terrane reviewed: UPb zircon geochronology and provenance studies provide paleotectonic links with a growing Proterozoic Amazonia

Abstract New and compiled data of zircon U Pb ages and geochemical-isotopic constraints provide new insights into the orogenic evolution of the Rio Apa Terrane (RAT) and its close affinity with the Amazonia throughout the Proterozoic. Two terranes with distinct evolutionary histories built the RAT. The Porto Murtinho (2070–1940 Ma) and Amoguija (1870–1820 Ma) magmatic arcs generated the Western Terrane which is mainly composed of short-lived crustal components. Granitoid rocks (1870 Ma) in the distal Corumba Window indicate that the RAT is much larger in extent. The Caracol accretionary arc (1800–1740 Ma) and the associated Alto Terere back-arc basin formed away from the Amoguija belt, being roughly coeval with the adjoining Baia das Garcas suite (1776 Ma) and Paso Bravo granitoid rocks (1774–1752 Ma). These tectonic units constitute the Eastern Terrane, whilst the Nd Hf isotopic constraints indicate derivation from a predominantly juvenile magma source with the minor input of crustal-derived contaminants. The youngest detrital zircon grains from the Alto Terere samples gave 1740–1790 Ma ages and unimodal age spectra were mainly present. The basin infill was, therefore, most likely concomitant with the exhumation of the Caracol belt. Alto Terere provenance study also included detritus from passive to active margin settings. The RAT underwent regional cooling between 1.35 and 1.27 Ga, documented mainly by 40Ar 39Ar and K Ar ages. This age pattern matches a collisional episode that formed the accretionary margin of Amazonia, suggesting that the RAT was a close neighbor at Ectasian times. The geodynamic interplay between them lasted until 1.1 Ga ago, highlighted by some shared-components of a LIP event.