Post-collisional, high-Ba-Sr Teixeira Batholith granites: Evidence for recycling of Paleoproterozoic crust in the Alto Pajeú domain, Borborema Province – NE-Brazil

Abstract

Late-Neoproterozoic granitoids of diversified nature and ages (640–525 Ma) are widely distributed in the Borborema Province and their petrogenesis can provide important insights about the Brasiliano/Pan-African Orogeny (ca. 650–550 Ma). The Neoproterozoic Teixeira Batholith comprises an ENE – elongated intrusion of c. 800 km2 emplaced in metasedimentary rocks and orthogneisses in central Borborema Province immediately south of the Patos Shear Zone. Textures and modal mineral percentage allow to divide the batholith into six petrographic facies, ranging in composition from monzogranite to quartz syenite, containing less than 10% of modal mafic mineral phases (amphibole ± clinopyroxene and biotite). Titanite, epidote, apatite, zircon and Fe-Ti oxide are the main accessory phases. LA-ICP-MS U-Pb zircon data from four facies yield ages ranging from 585 to 600 Ma, like other Neoproterozoic pre- to early-transcurrent intrusions related to the Brasiliano orogeny. The granitoids belong to the magnetite series, are metaluminous and have high-K calk-alkaline to shoshonitic affinities. Major and trace elements data are typical of granites originating from high barium‑strontium (HiBaSr) magmas, i.e., high Ba (1825–7370 ppm), Sr (1110–2530 ppm), low Rb (56–137 ppm), Th (1.6–15.8 ppm), Nb (6.2–34.7 ppm), Y (3.7–33.2 ppm) and HREE contents (Gd-Lu: 3.64–24.36 ppm). The granitoids have negative ƐNd(590Ma) (−13.68 to −16.04) and ƐHf(t) (−16.27 to −20.80) values, and Paleoproterozoic Nd and Hf TDM model ages ranging from 2.08 to 2.23 and 2.3 to 2.6, respectively, similar to the ages of basement rocks of the Central subprovince. The isotopic data and trace elements signature suggest magma generation by partial melting of Paleoproterozoic mafic/intermediate lower crust, leaving a plagioclase-free and garnet and/or amphibole-bearing residue. Partial melting occurred after a long period of contractional tectonics, and predated development of the Patos shear zone by ca. 20 Ma.