Work

AMS fabrics and geochronology (U-Pb, 40Ar/39Ar) of peraluminous Banabuiú pluton record crustal extrusion in the northern Borborema Province (NE Brazil)

Year: 2026

Type: article

Abstract: Post-collisional lateral escape tectonics in the Borborema Province (NE Brazil) is characterized by a complex interplay between ductile shearing and syn-kinematic magmatism. We investigate the emplacement fabrics of the Banabuiú pluton, a peraluminous granite associated with pegmatite dikes, to reconstruct the kinematic evolution of a wedge-shaped crustal domain bounded by ductile shear zones. An integrated approach combining Anisotropy of Magnetic Susceptibility (AMS), Anisotropy of Anhysteretic Remanent Magnetization (AARM), U-Pb zircon geochronology and 40 Ar/ 39 Ar mica thermochronology was used to examine the relationship between pluton emplacement at the intersection of sinuous shear zones. Zircon U-Pb dating identifies two magmatic pulses at ca. 585 ± 3 Ma and ca. 565 ± 2 Ma, whereas the host migmatitic gneiss yields a c.a. 2.1 Ga age, overprinted by high-grade metamorphism in the range of 616-590 Ma. The low magnetic susceptibility values (K mean = 61.3 x 10 -6 SI), together with thermomagnetic and hysteresis data, indicate that paramagnetic minerals dominate AMS signal of the pluton, with minor contributions of ferromagnetic phases (magnetite, hematite). Magnetic foliations are concentrically distributed in the central part of the pluton and contain well-defined NNE-trending lineations. Subsequent cooling and transition to a brittle deformation were accompanied by the emplacement of Li-rich pegmatite dikes, which yield 40 Ar/ 39 Ar mica ages ranging from of 512-508 Ma. The results are consistent with a dextral zipper-like model for the southward extrusion of the crustal wedge, which accommodated the emplacement of the Banabuiú pluton. Late cooling and exhumation promoted the development of extensional and shear fractures in the pluton and host rocks, which subsequently acted as conduits for pegmatitic emplacement.

Source: Journal of Structural Geology

DOI: 10.1016/j.jsg.2026.105815

Authors: Kauê Seoane, Carlos J. Archanjo, Maria Helena B.M. Hollanda, Luciano da Silva, Maria Irene B. Raposo

Institution: Universidade de São Paulo

Language: English

Topic: Geological and Geochemical Analysis

Subfield: Geochemistry and Petrology

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,380

Funders: Fundação de Amparo à Pesquisa do Estado de São Paulo, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico