Zircon geochronology of granitoids from the western Bacajá domain, southeastern Amazonian craton, Brazil

Abstract

New zircon U–Pb SHRIMP and Pb-evaporation data on rocks from the west part of the Bacaj´a domain, southeastern Amazonian craton, reveal crustal evolution marked by a succession of magmatic events from Neoarchean to Orosirian. This domain represents the southern part of a geochronological province of the Amazonian craton that evolved during the Trans-Amazonian cycle (2.26–2.0 Ga). The earliest event is represented by inliers of ca. 2.67, 2.5 and 2.45 Ga orthogneisses and supracrustal rocks, followed by the formation of a 2.36–2.34 Ga granitoid-greenstone terrane and 2.31 Ga granitoids. Rhyacian granitoids and charnockitic rocks marked the main evolutionary|stages of the Bacajá domain. Rhyacian magmatic events were distinguished in this domain: 2.21, 2.18, 2.16–2.15 and 2.13 Ga granitoids related|to magmatic arcs of the Trans-Amazonian orogenies; 2.10–2.09 and 2.08–2.07 Ga granitoids and charnockitic rocks related to the post-collisional|stage. A younger magmatic event at 1.99 Ga remains controversial, as it is uncertain whether this represents the last magmatic pulse of the|Trans-Amazonian cycle or whether it is related to a younger cycle which affected the adjacent domain|Although Archean rock remnants have been found in Trans-Amazonian domains from South America, Siderian rocks are rare and distinguish the Bacajá domain from other Trans-Amazonian orogens of the Amazonian craton