Reassessing the Cariris Velhos Event: Evidence for a Compressive Tectonic Setting in the Borborema Province, NE Brazil

Accretionary orogenesis comprises some of the most fundamental processes responsible for the construction of the lithospheric crust throughout geological time. The Cariris Velhos event, which is doccumented between 1000 and 920 Ma, represents one of the most debated topics regarding the Neoproterozoic evolution of the Borborema Province in northeastern Brazil. Although widely acknowledged for its significance, the geodynamic nature of this event remains under dispute, having been interpreted either as an accretionary-collisional orogeny or as an episode of lithospheric break-up attempt. Here, we support a compressive tectonic setting for the Cariris Velhos event, based on compiled geochemical and isotopic data (Sm–Nd and Lu–Hf) from metagranitic rocks of the Alto Pajeú Terrane (central Borborema), the Pernambuco-Alagoas Superterrane, and the Riacho do Pontal and Sergipano fold belts (southern Borborema). These rocks exhibit geochemical signatures characteristic of calcic to alkali-calcic and ferroan magmas, with some resembling magnesian Cordilleran-type granites. They also correspond to the classical meta- to peraluminous I-type and S-type granitoids. Spider diagrams reveal negative anomalies in high field strength elements (HFSE), such as Nb and Ta, typically associated with subduction-related settings in most modern orogenic belts worldwide. Chondrite-normalized rare-earth element (REE) patterns suggest a mixture of crustal and mantle-derived sources, mainly due to inheritance from a Paleoproterozoic reservoir, as well as crustal recycling during the Brasiliano Orogeny in the late Neoproterozoic. Tectonic discrimination diagrams based on low-mobility minor and trace elements further support a continental margin subduction setting. Calculated εNd and εHf values range from negative to slightly positive, indicating contributions from juvenile sources as well as reworking of older Meso- to Paleoproterozoic crust, consistent with the observed T_DM model ages. Although further investigation is necessary to fully resolve the nature of the Cariris Velhos event, we propose that it was, at least in part, an orogenic episode that may have coincided with continental break-up resembling modern continental arc to retro-arc foreland systems developed upon previously stabilized thick continental lithosphere.