A new record of continental arc magmatism in the Ceará Central Domain, Borborema Province (NE Brazil): evidence from the Pacatuba-Maranguape Complex

Abstract

The amalgamation of continental masses during the formation of West Gondwana at the end of the Neoproterozoic (ca. 0.6 Ga) resulted in the closure of oceans and associated generation of magmatic arcs. To better understand episodes of high magma production, compositional and isotopic evolution of arc magmatism in the western active margin of Gondwana, this work presents new U-Pb zircon ages, lithogeochemistry, whole-rock Nd and in situ zircon Hf isotopes from plutonic and metaplutonic rocks of a dismembered arc-related unit (Pacatuba-Maranguape Complex) from the Ceará Central Domain, Borborema Province (NE Brazil). The Pacatuba-Maranguape Complex is exposed in the northeastern portion of the Ceará Central Domain and comprises pre- to late-tectonic granitoids bordered by migmatitic-gneisses that have experienced variable partial melting and deformation. Zircon U-Pb analyses yielded concordant ages of 675 Ma, 655–640 Ma, 630–625 Ma and 610 Ma, with inherited grains of 880–700 Ma, 700–650 Ma and 2200–2000 Ma. Geochemically, the granitoids are medium- to high-K calc-alkaline, metaluminous to slightly peraluminous, magnesian and calc-alkalic to alkali-calcic. Lu-Hf and Sm-Nd model ages provided TDM (Hf) model ages between 920 Ma and 1470 Ma with ɛHf(t) values of + 12.75 to −5.44, and TDM (Nd) values between 950 Ma and 1470 Ma with ɛNd(t) values between −1.06 and + 4.35. These data indicate that these granitoids were generated from the mixture of juvenile magmas and older crustal components on an active continental margin setting. Petrogenetic and geochronological constraints indicate a synchronous evolution with the Santa Quitéria Magmatic Arc, exposed approximately 100 km to the west. The compilation of geochronological and geochemical data from the Pacatuba-Maranguape Complex and the Santa Quitéria Arc suggests that arc magmatism developed mainly as a result of a magmatic flare-up between 660 and 620 Ma during the subduction of the Goiás-Pharusian oceanic crust in the central portion of West Gondwana.