Reappraisal of the Sumé Complex: geochemistry and geochronology of metaigneous rocks and implications for Paleoproteorozoic subduction-accretion events in the Borborema Province, NE Brazil

Abstract

The Alto Moxotó Terrane represents the largest exposure of Paleoproterozoic rocks in the central Borborema Province. Several medium-to high-grade metamorphic units are described in the terrane, however geochronological data are still scarce, and the main periods of crust buildup and recycling are poorly known. In this study, we investigate the nature and age of metagranitic and metamafic-ultramafic rocks in the type area of the Sumé Complex. U-Pb zircon data from a metasyenogranite yields a concordant age of 1.97 Ga, which is in contrast with the previously published age of the complex (c. 640 Ma). In addition, Sm-Nd isotope signature indicates Paleoproterozoic to Mesoarchean sources that coupled with negative εNd(t) values suggest reworking of a preexisting crust. Whole-rock geochemical data indicate that metamafic rocks are similar to those already described in the terrane, corresponding to island-arc tholeiites, whereas the metagranitic rocks share similarities with magmas that were generated in an evolved stage of an orogenic setting. The obtained results are coherent with a long-lived Paleoproterozoic accretionary-collisional event (c. 2.1-1.9 Ga) described in the Borborema Province, which is correlative with Paleoproterozoic (c. 2.2-2.0 Ga) basement inliers/terranes from Pan-African Fold belts..

Description and hierarchy of ductile deformation events in the Camalaú region, state of Paraíba, central portion of the Alto Moxotó Terrane, Borborema Province, Brazil

“…Considering that a younger episode has not been clearly described yet for neosomes and even gneissic domains of the Alto Moxotó Terrane, up to now, such correlation is unlikely and merely speculative. The D 2 deformation markers identified in this study correspond to thrust/tangential tectonics, described as similar to Alpine/ Himalayan nappes (Santos et al 2017a), and are better preserved in other areas of the Alto Moxotó Terrane, such as the Sumé Region (Santos and Santos 2019). In the studied area, we assume that crustal shortening produced inclined to recumbent and close to isoclinal folds in the core of the orthogneiss sheets, also producing local migmatization.…”