Geochemistry, geochronology, and tectonic aspects of the Angicos plutonism: Insights into equigranular high-K calc-alkaline magmatism in the northern Borborema Province

Abstract

The Borborema Province is renowned for its prominent Ediacaran to Cambrian plutonism, constituting more than 15 % of its total area. Within this context, the Angicos Batholith is a NNE-trending elongated pluton with ca. 250 km², representing one of the largest bodies with equigranular texture in the northern part of the province. On the northwestern margin of the batholith, the Poço da Oiticica Stock forms a N-S elongated intrusion, while the NW-SE semicircular Flores Stock is situated on the northeastern side. Both exhibit compositions and textures like those of the batholith. Despite its volume, the understanding of the granitogenesis in this area remains limited due to a lack of comprehensive data concerning geochemistry, geochronology, and geological-geophysical mapping approaches. In this study, we present a new analytical dataset of Angicos Plutonism combined with remote sensing and aerogeophysical data to assist in geological-structural mapping. The equigranular granites are composed of orthoclase (Or_96-90Ab_4–10), oligoclase (An_21-17Ab_77-81Or_2–1), and Fe-biotite with smaller amounts of magnetite, ilmenite, apatite, allanite, monazite, fluorite, and zircon. These rocks exhibit SiO₂ contents ranging from 70 to 75 wt%, total alkalis from 8.8 to 9.0 wt%, and weakly peraluminous compositions. The batholith has enrichment in large ion lithophile elements and depletion in high-field strength elements. The light rare earth elements content is high [4 ≤ (La/Sm)_N ≤ 11], combined with negative Eu anomalies (Eu/Eu* = 0.4–0.9) and a fractionated spectra of heavy rare earth elements [4.2 ≤ (Gd/Yb)_N ≤ 7.7]. The newly obtained U-Pb age of 584.8 ± 0.9 Ma on the southern side of the body is compatible with the peak of plutonic activity in the northern Borborema Province. The compositional and textural similarity between the Angicos granites and younger neighboring stocks (∼550–530 Ma) highlight a long-lived period of high-K calc-alkaline magmatism in the region, with the Angicos Batholith representing one of the oldest members of this suite. The geochemical signature combined with the presence of xenoliths of banded gneisses along with inherited zircons of the Rhyacian Period, suggests crustal recycling in the region, where metaplutonic rocks of the Caicó Complex would be the main source of granites. The equigranular texture of such a large pluton would be justified by high undercooling rates. In this context, the extensional bridging accommodation mechanism in laterally alternating shear zones emerges as a plausible model for the emplacement of the Angicos Batholith.