U–Pb detrital zircon provenance of metasedimentary rocks from the Ceará Central and Médio Coreaú Domains, Borborema Province, NE-Brazil: Tectonic implications for a long-lived Neoproterozoic active continental margin

Abstract

U–Pb geochronological analyses have been acquired on detrital zircon grains collected from 14 samples in the Ceará Central (CCD) and Médio Coreaú (MCD) tectonic domains, separated by the Transbrasiliano-Kandi Lineament (TKL) on the Borborema Province. To the West of this lineament, the basement of the MCD has a tectonic affinity with the West African and São Luis Cratons, where Paleoproterozoic rocks predominate. Within this area, three samples of the São Joaquim quartzite yielded Paleoproterozic and Archean ages only, with the youngest 206Pb/207Pb ages at ca. 1750Ma. However, the Goiabeira Formation schist, in the same domain, yielded younger 207Pb/235U ages around 720Ma, with predominance of zircons within the 750–1100Ma interval. To the East of the TKL, the Borborema Province correlates well with the Transaharan Belt of West Africa, where the Paleoproterozoic-Archean basement was affected by a strong tectonic imprint of the Neoproterozoic Brasiliano-Pan African orogeny. Three samples from the region between the TKL and the Tamboril-Santa Quitéria granitic–migmatitic Complex (TSQgmC) yielded younger 207Pb/235U concordant ages (ca. 660–700Ma), which are 20–60Ma younger than those of the Goiabeira Formation. Further east within the CCD, eastern of the TSQgmC, six samples yielded two distinct detrital patterns, with some samples showing younger concordant ages (ca. 900 and 750Ma), while others demonstrate a strong Paleoproterozoic source component with zircons older than ca. 1500Ma. Finally, one sample of the post-collisional extensional Jaíbaras Trough, within the main axis of the TKL, yielded a maximum deposition age of ca. 540Ma, with a strong source component ranging from 540 to 640Ma, derived mainly from the TSQgmC. Evidence of a large ocean basin prior to 800Ma, along the vicinity of the TKL, is well established in Central Brazil and West Africa. We believe that the strong source component at around 800–700Ma, and possibly also the older ones at ca. 1000Ma, were shed from magmatic arc systems developed at the margins of the ancient continent which makes up the basement of the Borborema Province. Abrupt cessation of the detrital zircons input at ca. 650Ma, suggests a change in the tectonic regime at this time, marking the onset of collisional tectonics and main metamorphism in the province. This fact is supported by the ages spanning the 640–590Ma interval found in the metamorphic domains of the studied zircons which are partially synchronous with the development of the main tectonic and magmatic stages of the TSQgmC.