Fabric- and fluid-constrained ⁴⁰Ar/³⁹Ar geochronology of the northeastern Carajás Province, Amazonian Craton: separating hydrothermalism from Rhyacian and Orosirian reworking of Archean crust

Felipe Mattos Tavares , Rudolph Allard Johannes Trouw, Paulo Vasconcelos

The Carajás Province, southeastern Amazonian Craton, is a polycyclic Archean block in which the ages of rocks, hydrothermal minerals and tectonic fabrics need not coincide. We integrate multiscale structural analysis with fabric-constrained ⁴⁰Ar/³⁹Ar geochronology of amphibole, biotite and white mica selected from mapped fabrics or well-defined hydrothermal assemblages. Although the province preserves a dominantly Archean rock record, minerals defining its main foliation yield Paleoproterozoic recrystallization ages. Hornblende and biotite tied to that fabric record a Rhyacian Transamazonian event at ca. 2.08–2.05 Ga. A distinct Early Orosirian Sereno event at ca. 2.01–1.96 Ga is recorded by anthophyllite–tremolite and biotite, whereas white mica near Serra Pelada yields ca. 1.93 Ga minimum constraints partially reset toward a ca. 1.88 Ga Uatumã overprint. Hydrothermal amphiboles preserve a polyphase Neoarchean record. Substantial Serra Verde fractions overlap the Re–Os molybdenite age, and the principal surviving amphibole reservoirs yield 2516 ± 14 and 2517 ± 12 Ma. In the stretched FT-009C hydrothermal pocket, exploratory arrays at 2199 ± 25 and 2087 ± 31 Ma record selective fluid-assisted re-equilibration and deformation-related recrystallization. Cl/K systematics identify fluid-hosted excess ⁴⁰Ar and separate inherited reservoirs from geological age components. The exposed architecture is therefore an Archean crustal block pervasively reworked during distinct Paleoproterozoic events, with domain-scale recrystallization controlling the survival of older argon reservoirs.