Fragments of juvenile Siderian continental crust in the Rio Piranhas-Seridó Domain, Borborema Province, Northeastern Brazil, as deduced by zircon U-Pb and whole-rock Sm-Nd systematics

Abstract

In the Rio Piranhas-Seridó Domain (PSD), Borborema Province, geological mapping and aerogammaspectrometric data, combined with studies of Sm-Nd isotopes in whole rock and U-Pb in tonalitic orthogneiss and metamorphic clinopyroxene-hornblendite zircons enabled the identification and individualization of geological units with crystallization ages of 2456 ± 4 Ma and 2381 ± 16 Ma, respectively (U-Pb in zircon). These Siderian rocks are part of the basement of the central and northern portions of the PSD and are called the Arabia Complex. The tonalitic orthogneiss has an Sm-Nd (TDM) model age of 2.56 Ga, with an εNd value of +1.20, which allows inferring a juvenile source for the magma that gave rise to the protoliths of the rocks from the Arabia Complex. The identification and improvement of the geological cartography of Siderian units in the central portion of the PSD has contributed to a better understanding of the events of juvenile crust generation for the Borborema Province in general and inserts the province in the worldwide debate on geotectonic evolution during the Siderian Period.