Implications of the Dominant LP–HT Deformation in the Guanhães Block for the Araçuaí West-Congo Orogen Evolution

The Aracuai-West Congo Orogen is the result of convergence between the Sao Francisco and Congo cratons during the assembly of West Gondwana. Within this orogen, the Aracuai Belt in SE Brazil reflects the western external domain. The Aracuai Belt is characterized by major east-dipping structures and high- to medium pressure metamorphic rocks developed during crustal thickening at ca. 585-560 Ma and are juxtaposed along crustal-scale structures to the crystalline core of the orogen. The Guanhaes Block in the southern Aracuai Belt is characterized by higher metamorphic grade and dominantly shallowly west-dipping structures compared to the neighboring tectonic domains. While several studies have focused on the evolution of the axial crystalline core of the Aracuai orogen and on the early collisional stages in the Aracuai Belt, little attention has been given to the structural and metamorphic history of the poorly studied Guanhaes Block. The supracrustal rocks in the central Guanhaes Block record two tectono-metamorphic stages: D-2/M-2 and D-3 /M-3, with potential D-1/M-1 relicts rarely preserved within D-2/M-2 low-strain domains. The D-2/M-2 overprinting stage is associated with the development of a dominant, shallow axial planar foliation (S-2) of isoclinal F-2 folds under low-pressure and high-temperature (LP-HT) conditions (ca. 6 kbar and 750 degrees C). During this D-2/M-2 stage continuous segregation of syn-kinematic partial melting and generation of granitoid rocks occurred. The 530 Ma, syn- D-2/M-2 granitoid has negative epsilon Hf-(i) at ca. -32 which indicates the source of magma from melting of older, isotopically evolved, Archaean or Paleoproterozoic crust. U-Pb geochronology on monazite, titanite and hydrothermal zircon constrain the retrograde D-3/M-3 event at ca. 510 Ma. The Guanhaes Block uniquely records dominant deformation under LP-HT metamorphic conditions during the late-orogenic stages and its evolution could have important tectonic implications for the concurrent models suggested for the late Neoproterozoic Aracuai-West Congo Orogen. (C) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.