Platform and back-arc basins during the Gondwana Collage: Andrelândia Group and Paraíba do Sul Complex (Brazil)

This work aims to analyze data of U–Pb and Lu–Hf isotopes (by LA-ICP-MS) on detrital zircons from the Andrelândia Group and Paraíba do Sul Complex to study the tectonic evolution of the Guaçuí Shear Zone (GSZ), southeastern Brazil. This study also aims to investigate if the GSZ is a possible suture zone between two terrains: the Andrelandia Group, located west of the GSZ, and the Paraíba do Sul Complex, located east of this structure. Metasedimentary samples collected from these two areas were classified as follows: biotite gneiss, biotite gneiss and impure quartzite. From the U–Pb age-based probability histograms, it was found that the Andrelandia Group has a maximum sedimentation age of 2099 ± 7 Ma and comprises metasediments composed mainly of Paleoproterozoic sources deposited in a platform environment and that the Paraíba do Sul Complex has a maximum depositional age of 666 ± 1 Ma, and contains Neoproterozoic-aged sources deposited in a back-arc basin. Both complexes record metamorphism events marked at 590 ± 6 Ma and 605 ± 14 Ma, respectively. The initial 176 Hf/ 177 Hf isotopic ratios from the Andrelândia Group ranged from 0.280817 to 0.282069 and Ɛ Hf(t) values varied between − 39.3 and 13.7. The ages of the depleted mantle model (T DM ) obtained for the Andrelândia Group ranged from 3.5 to 1.8 Ga, with a concentration around 2.3 Ga. The analyzed samples from the Paraíba do Sul Complex presented a large variation of the initial 176 Hf/ 177 Hf values, ranging from 0.281009 to 0.283139. The Ɛ Hf(t) values found in this group varied between − 24.2 and 42.3 and the T DM values show a wide variation of ages. The maximum T DM age found for the Paraíba do Sul Complex was ≈ 3.6 Ga and youngest age was ≈ 0.66 Ga, with a concentration between 2.0 and 1.8 Ga. The T DM ages are older in the Andrelândia Group than in the Paraíba do Sul Complex, which indicates that these complexes are not chrono correlated, but register the same deformational process related to the Brasiliano event. These results support the hypothesis that the Rio Negro Magmatic Arc was a suture zone between these two terrains, which record the same deformational and collisional events.