The Serrinha granite-greenstone terrane revisited: A reevaluation of its evolution based on the current U–Pb age database

This paper aims to summarize the current knowledge of the Serrinha Nucleus and add new U–Pb geochronological data for this area. New ages were obtained for granitoids and a metadacite belonging to the Felsic Volcanic Unit of the Rio Itapicuru Greenstone Belt (RIGB). The age of 3185 ± 9 Ma obtained at the Pedra Alta granodiorite-tonalite pluton corresponds to the interval of emplacement (2.9–3.2 Ga) of the TTG granites in the Serrinha Nucleus during the Archean. As expected for granites belonging to the Paleoproterozoic TTG/calc-alkaline group, Barrocas and Lagoa dos Bois plutons yielded U–Pb zircon ages of 2168 ± 12 Ma and 2158 ± 13 Ma, respectively. These 2.15–2.17 Ga ages are attributed to a syn-orogenic evolution of the calc-alkaline felsic volcanism of the RIGB during the Rhyacian period, which is related to the closure of the Itapicuru basin. A sample of a biotite-granite dyke collected at the Araci TTG Pluton, which also is part of the Archean TTGs group of granites, yields an age related to the post-orogenic Morro do Lopes magmatism. Its age of 2076 ± 6 Ma also coincides with those attributed to the hydrothermal event that resulted in the gold mineralization at the RIGB and reinforces the widespread efects of this thermal post-orogenic alkaline magmatic event. The metadacite age of 2147 ± 38 Ma is considered the minimum crystallization age for the felsic volcanic arc of the RIGB, being compatible with regional ages obtained for other metavolcanic rocks and granitoids from this area. The ages obtained in the present work, added to the geochronological database of Serrinha Nucleus, show that the closure of the Itapicuru basin occurred between approximately 2.15 and 2.17 Ga, period corresponding to the first deformation phase that affected the orogen. The age obtained for the intrusive Barrocas Pluton (2168 ± 12 Ma), which outcrops at the southern tip of the greenstone, suggests that the volcanic-sedimentary rocks of Itapicuru should be older and highlights a new model for the evolution of Serrinha Nucleus and the concept of the “Rio Itapicuru Greenstone Belt”.