Definition of magmatic suites in ediacaran bodies of the NE Province Borborema (state of Rio Grande do Norte): Pitombeira, Taipu and Gameleira Plutons

Abstract

The Pitombeira, Taipu and Gameleira plutons, located in the northeasternmost portion of the São José do Campestre Domain within the Borborema Province (NE, Brazil), are subjects of lithogeochemical studies in the present work. The Pitombeira Pluton comprises a monzo- to syenogranitic facies defined by K-feldspar phenocrysts, and a quartz-dioritic to tonalitic facies, mainly as enclaves, with laths of plagioclase showing compositional zoning and chilled rims. The Taipu Pluton is made of equigranular, locally porphyritic, monzo- to syenogranites, whereas the Gamaleira Pluton encompasses tonalitic and granodioritic rocks with porphyritic textures and compositionally zoned plagioclase crystals. Geochemical discriminant diagrams reveal that the rocks forming the Gameleira Pluton are metaluminous, with a calc-alkaline signature and magnesian character, contrasting with the subalkaline (high-K calc-alkaline) signature and ferroan character of the Taipu and Pitombeira Plutons, where the former is highly peraluminous and the latter is metaluminous to slightly peraluminous. Rare Earth Elements patterns are similar to all plutons and register negative Eu anomalies and a relative enrichment of LREE over HREE, with LaN/YbN ratios between 9.38 to 16.20 (Gamaleira Pluton), 17.99 to 31.39 (granitic facies of the Pitombeira Pluton), 14.15 to 21.81 (dioritic facies of the Pitombeira Pluton) and 15.17 to 175.41 (Taipu Pluton). Based on the combined investigation of structural, textural and geochemical data, a late- to post-collisional tectonic environment is suggested for the plutons here studied.