Thermochronology and Exhumation History of the Basement and Plutonic Rocks of the Borborema Province, Brazil

Abstract

The Borborema Province is subdivided into the following tectonic domains: São José do Campestre, Rio Piranhas–Seridó, Jaguaribeano, Central Ceará, and Médio Coreaú. Fourteen zircon samples separated from Brazilian-age plutonic rocks within these domains were analyzed using both the Fission Track Method (FTM) and U–Pb dating via LA-ICP-MS. Standard zircon reference materials - Fish Canyon Tuff (FCT) and Kawamoto Granodiorite (OD-3) - were also dated to validate the results obtained from 487 zircon grains. The novel fission track laser ablation (FTLA) ages determined for each tectonic domain are as follows: São José do Campestre (189 ± 6 Ma, 265 ± 8 Ma, ~288 ± 9 Ma); Rio Piranhas–Seridó (411 ± 12 Ma, 279 ± 9 Ma, 233 ± 8 Ma, 197 ± 6 Ma); Jaguaribeano (371 ± 11 Ma, 214 ± 8 Ma); Central Ceará (~261 ± 8 Ma, 192 ± 7 Ma); and Médio Coreaú (321 ± 11 Ma). Some samples exhibit multiple FTLA age populations, indicating complex thermal histories. These varied fission track ages suggest significant post-intrusion tectonic activity followed by exhumation, likely related to pre-Atlantic rifting events affecting the South American Platform. Complementary U–Th/He analyses on 16 zircon grains yielded ages ranging from 165 to 350 Ma, corroborating the presence of distinct FTLA age populations and reflecting the progressive cooling of the plutonic bodies. Most U–Pb zircon ages are consistent with the Brazilian orogenic event, aligning with previously published data. Collectively, these results highlight the role of multiphase tectonic reactivation and allow for the reconstruction of the thermal and tectonic evolution of the Borborema Province using a multi-chronometer approach.

Keywords: Zircon Mineral, Fission Track Method, U-Pb system. Geochronology, U-Th/He Method, Borborema Province.