The Orosirian Cuiú-Cuiú magmatic arc in Peixoto de Azevedo domain, Southern of Amazonian craton

Abstract

The Peixoto de Azevedo domain (PAD) is the southernmost portion of the Tapajós-Parima province in the Amazonian craton. It is constituted by Paleoproterozoic rocks (2.05–1.85 Ga) of the Cuiú-Cuiú magmatic arc (CCMA), and by post-orogenic to anorogenic granitoids. The rocks with magmatic arc signature in the PAD are correlated with those of the Mundurucus orogeny (2.04–1.96 Ga) in the Tapajós domain, where several authors propose the evolution of at least three magmatic arcs. However, in this work, the rocks of PAD are interpreted as part of a single magmatic arc of Orosirian age, the CCMA. Geochronological, geochemical and petrographical data suggest that CCMA has evolved within a continuous long-lived subduction process, in the approximate range of 2.05–1.95 Ga, at the border of an Archean terrain. This older basement is represented by the Gavião gneiss, an inlier whose U-Pb LA-ICP-MS zircon age is 2825 ± 9 Ma. Additionally Nd-TDM data (2.76–2.5 Ga) and some Archean inherited and detrital zircon crystals indicate that CCMA developed on an Archean basement. The CCMA is divided into: Cuiú-Cuiú complex (CCC; 2050–1990 Ma), which marks the main phase of subduction in the evolution of CCMA and is represented by migmatitic orthogneisses, quartz diorites, tonalites and granodiorites; metaplutonic Pé Quente suite and volcanic rocks of the Jarinã formation (2000–1970 Ma), which both form an expanded calc-alkaline serie, typical of continental margin arcs, of tonalitic, granodioritic, monzo- and syenogranitic composition; and Nhandu intrusive suite (1970–1950 Ma), composed of high-K calc-alkaline to shoshonitic syeno- and monzogranites, whose isotopic data (ϵNd from −0.95 to −7.6) indicate strong participation of crustal sources in its generation. Nhandu intrusive suite shows chemical characteristics of magma generated in late to post-tectonic setting and marks the final phase of the CCMA evolution. The metamorphic peak in the area reached high amphibolite facies, probably between 2015 Ma and 1990 Ma (main age range of the migmatitic gneisses). After the orogenic compressive phase, the region experienced tectonic quiescence, which was followed by post-orogenic to anorogenic extension, approximately between 1905 and 1850 Ma. This later event is represented by expressive acid plutonism of Guarantã do Norte and Matupá granitoid suites, and subordinately by basic rocks of Flor da Serra intrusive suite.