The Trairão area as a boundary between geochronological provinces of the Amazonian craton based on U–Pb and Sm–Nd data from two flare-ups

The Trairão area, in the central Amazonian Craton, records extensive Orosirian volcano-plutonic events dominated by acid and subordinate intermediate rocks. U–Pb laser ablation inductively coupled plasma mass spectrometry zircon geochronology reveals two magmatic flare-ups separated by a c. 100 Myr lull: (1) a plutonic-dominated phase at c. 1980 Ma; (2) a volcanic phase at c. 1880 Ma. Previous geochemical data distinguish calc-alkaline and alkaline suites, positioning Trairão as a key area for re-evaluating geotectonic boundaries. Sm–Nd whole-rock analyses ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ε</mml:mi> </mml:math> Nd ( t ) = −1.39 to −7.11; Nd-T DM = 2.31–2.64 Ga) indicate magma derivation from mixed Archean and juvenile Paleoproterozoic sources. These results define a NW–SE boundary separating the Tapajós (Nd-T DM &lt;2.5 Ga) and Iriri–Xingu (Nd-T DM &gt;2.5 Ga) domains, correlating with the Ventuari–Tapajós and Central Amazonia provinces, respectively. We propose that the Orosirian Tapajós Domain magmatic arc was accreted onto the Iriri–Xingu continental domain, followed by extensional alkaline magmatism (silicic large igneous province).