A-Type Post-Collisional Granites in the Borborema Province - NE Brazil: The Queimadas Pluton

The Queimadas Pluton constitutes an E-W elongated tabular intrusion, exposed over an area of 50 km2. It is intruded in Paleoproterozoic gneiss-migmatite of the Alto Pajeْ Terrane in the Central Tectonic Domain of the Borborema Province, and has a zircon U-Pb age of 570±20 Ma. It is cut by later shear zones with NNE direction, which provoked necking and disruption in the body. A suite of biotite±amphibole monzogranites, associated with quartz diorite and later leucogranite and diabase, dominates in these alkaline granites that are metaluminous to slightly peraluminous and show high FeOt/(FeOt + MgO) and K2O/Na2O ratios. Their REE patterns are moderately fractionated, with (Ce/Yb)N ratios of 10-16 and significant negative Eu anomalies (Eu* = 0.40-0.67). Geochemical and Nd isotopic data indicate that the Queimadas Pluton magma originated by partial melting of a crustal fertile granodioritic rocks. The studied granites crystallized under relatively low fO2 and are A-type post-collisional granitoids.