The clastic record of an early Brasiliano Orogeny: pre-collisional subduction-related metamorphism within the southern Borborema Province through detrital rutile analysis

Abstract

The ubiquity of detrital zircon in clastic sediments made zircon one of the primary minerals for provenance and tectonomagmatic studies. However, its high U–Pb closure temperature (>900°C), limited growth of new zircon under upper amphibolite–eclogite facies, inherited bias towards felsic sources and refractory behaviour rarely representing first-cycle sedimentation can hamper the detection of key tectonomagmatic events. Other mineral assemblages, such as rutile, which formed in medium- to high-grade metapelite and metabasite during high-pressure and low-temperature subduction metamorphism can help to provide a complete record of polyphase orogenic evolution. In this study, we present U–Pb ages and trace elements in detrital rutile from the Ordovician Tacaratu Formation (Tucano–Jatobá Basin) to track the complete polyphase evolution of southern Borborema Province. Coupled U–Pb detrital zircon and rutile analysis revealed that detrital zircon ages lag detrital rutile ages by c. 100 myr. Three rutile age peaks at c. 767, 669 and 595 Ma were recognized, agreeing with subduction in magma-poor orogenic phases (lulls) between relatively high magma generation phases (flare-ups). The detrital rutile ages record earlier phases of Brasiliano Orogeny in southern Borborema Province (subduction-related metamorphism; closure of Sergipano Ocean), as this orogeny culminated in the collision of blocks followed by high-temperature metamorphism.