Geocronologia e evolução crustal da área do depósito de Cu-Au Gameleira, Província Mineral de Carajás (Pará), Brasil

Abstract

The Gameleira Cu-Au deposit is hosted by rocks of the Igarapé Pojuca Group, Itacaiúnas Supergroup, Carajás Mineral Province, southeastern Amazonian Craton. This group is represented mainly by mafic metavolcanic rocks (MVR), amphibolite, biotite schist, banded iron formation and/or hydrothermalite and cut by intrusive mafic rocks (IMR) as well as by deformed Itacaiúnas granites of Archean age (2.56 Ga) and Pojuca and Gameleira granites of Proterozoic age (1.87 and 1.58 Ga). Zircon crystals from a saprolite (2615 ± 10 Ma and 2683 ± 7 Ma) and from an IMR sample (2705 ± 2 Ma) are coeval with those from gabbros of the neighboring Águas Claras deposit. Pb-Pb dating of whole rock samples and chalcopyrite from the MVR indicated ages of 2245 ± 29 Ma and 2419 ± 12 Ma, respectively, while leached chalcopyrite yielded ages of 2217 ± 19 Ma and 2180 ± 84 Ma. These ages are interpreted as due to partial resetting provoked by the Proterozoic granitic intrusions or by tectonic reactivation along the Carajás and Cinzento strike slip systems or alternatively, as due to total resetting provoked by the last one. The TDM ages between 3.12 and 3.33 Ga for the MVR and IMR, and the initial Nd ε (t) values of –0.89 to –3.26 suggest continental contribution from older crustal material and possibly magma generation in a continental rift or active continental margin environment.