Evidence for 2.35 to 2.30 Ga juvenile crustal growth in the northwest Borborema Province, NE Brazil

Abstract: The c. 600 Ma Brasiliano Borborema Province of NE Brazil comprises a complex collage of Precambrian crustal blocks cut by a series of continental-scale shear zones. The predo-minant basement rocks in the province are 2.1–2.0 Ga Transamazonian gneisses of both juvenile and reworked nature. U–Pb zircon and Sm–Nd whole-rock studies of tonalite-trondhjemite-granodiorite basement gneisses in the NW Ceara ́ or Médio Coreau ́ domain in the northwestern part of the Borborema Province indicate that this represents a continental fragment formed by 2.35–2.30 Ga juvenile crust. This block has no apparent genetic affinity with any other basement gneisses in the Borborema Province, and it does not represent the tectonized margin of the c. 2.1– 2.0 Ga São Luis Craton to the NW. The petrological and geochemical characteristics, as well as the Nd-isotopic signatures of these gneisses, are consistent with their genesis in an island arc setting. This finding documents a period of crustal growth during a period of the Earth’s history which is known for its tectonic quiescence and paucity of crust formation. The study area is situated in the NW part of the Borborema Province (Almeida et al. 1981), NE Brazil, which formed as a result of Neoproterozoi