Tracing Neoproterozoic subduction in the Borborema Province (NE-Brazil): Clues from U-Pb geochronology and Sr-Nd-Hf-O isotopes on granitoids and migmatites

The Ceará Central Domain of the Borborema Province is a key tectonic domain within the 5000km-long West Gondwana Orogen, which extends from Algeria in Africa to Central Brazil. Igneous rocks of the Tamboril-Santa Quitéria Complex, investigated in this study, record a long-lived history of convergent magmatism and crustal anatexis. SHRIMP U-Pb dating and Hf-O isotope analyses of zircons from granitoids and migmatites, coupled with whole-rock Sr-Nd isotopes were used to constrain the evolution of this long-lived continental margin. Magmatism can be divided into three main periods: i) an early period comprising essentially juvenile arc magmatism at ca. 880-800Ma and continuing to 650Ma as evidenced indirectly by detrital zircons from syn-orogenic deposits, ii) a more mature arc period at ca. 660-630Ma characterized by hybrid mantle-crustal magmatic rocks, and iii) crustal anatexis at 625-618Ma continuing until ca. 600Ma. Detrital zircons with mantle values of δO¹⁸ (<5.7‰) in the range of 950 to 650Ma retrieved from fore-arc deposits indicate that juvenile input persisted throughout the evolution of the convergent magmatism. Juvenile and mature arc igneous rocks underwent anatexis that gave rise to extensive areas of diatexites within the complex. Anatexis overlap in time with the ages of (ultra)-high pressure (U)HP eclogitic metamorphism dated at 625-615Ma. In accordance with other continental collision zones, age of UHP/HP metamorphism is interpreted to mark the timing of continental collision and therefore indicate that the anatexis of arc rocks took place during continental subduction in a continent-continent collisional setting. Extensive migmatization continued until ca. 600Ma and are in part synchronous to the exhumation of the rocks to shallower crustal levels. Thus, the 350m.y. of magmatic activity in the Ceará Central Domain records the evolution of the West Gondwana margin of the Borborema Province from a juvenile arc setting through a mature arc and continental collision at around 625-600Ma.