Paleoproterozoic crustal evolution of the northern Borborema Province, NE Brazil: Insights from high-grade metamorphic rocks of the Canindé do Ceará Complex

Abstract

Archean to Paleoproterozoic crustal segments are widely recognized as basement inliers within the Neoproterozoic orogenic belts of the Pan-African/Brasiliano orogeny. For example, the Canindé do Ceará Complex, in the northern Borborema Province, NE Brazil, comprises a large domain of Paleoproterozoic high-grade metamorphic rocks with a protracted tectonic history. This complex is dominantly represented by sillimanite- and graphite-bearing metasedimentary rocks with associated tonalitic to granodioritic orthogneisses. All these rocks are highly deformed and variably migmatized. Minor granitic intrusions and lenses of garnet amphibolites are also present. In this work, in order to discuss the tectonic evolution of the area, we present new U-Pb LA-ICPMS zircon dating, Sm-Nd isotopes, and whole-rock geochemistry for selected samples of the Canindé do Ceará Complex. The amphibolites show tholeiitic affinity and Sm-Nd TDM model ages of 2.22–2.52 Ga with positive εNd(t), attesting to an oceanic signature. The tonalitic/granodioritic orthogneisses show U-Pb ages of 2.19 to 2.12 Ga, Sm-Nd TDM model ages of 2.16 to 2.34 Ga, which probably reflect arc-related environments. The collisional event is marked by granitic intrusions (aplites) and diatexites, which display U-Pb ages ranging from 2.08 to 2.03 Ga. This event is also recorded in zircon recrystallized from tonalitic/granodioritic rocks, which show U-Pb age at 2.04 Ga. Therefore, from our results and literature information, the Rhyacian/Orosirian basement rocks of the Canindé do Ceará Complex show a protracted evolutionary history, ranging from 2.2 to 2.1 Ga arc-related environments, to 2.1–2.0 Ga continental collision and late Neoproterozoic metamorphic overprint.