Produção Nacional
O MAGMATISMO ARQUEANO DA REGIÃO DE TUCUMÃ-PROVÍNCIA MINERAL DE CARAJÁS: NOVOS RESULTADOS GEOCRONOLÓGICOS
1999; Sociedade Brasileira de Geologia; Volume: 29; Issue: 4 Linguagem: Inglês
10.25249/0375-7536.1999294453460
ISSN2177-4382
AutoresValter Gama De Avelar, Jean Michel Lafon, Firmino Coutinho Coutinho Correia, Edésio Maria Buenano Macambira,
Tópico(s)Geochemistry and Elemental Analysis
ResumoNew geochronological determinations have been performed by the Pb/Pb method on zircons from Archean magmatic rocks of the Tucumã region in the Carajás Mineral Province (PMC). Zircons from a granodioritic orthogneiss of the Xingu Complex furnished an age of 2974 ± 15 Ma. Zircons from a felsic metavolcanic rock at the top of the Tucumã greenstones and an associated metagranodiorite gave ages of 2868 ± 8 Ma and 2852 ± 16 Ma, respectively. These results confirm that the principal episode of crustal growth in the southern part of the PMC took place between 3,0 and 2,85 Ga. The age of 2736 ± 24 Ma obtained for zircons from a syn-collisional granitoid indicate the time of the main deformational event of the Itacaiúnas shear belt (northern part of the PMC). Comparison of the available geochronological results for the PMC point out a distinct time-related evolution between the different regions.The southern part of the PMC behaved as a stable crustal block during the evolution of the Itacaiúnas shear belt between 2,74 Ga and 2,5 Ga. These new Pb/Pb results are systematically older than the previous Rb/Sr obtained on the same rocks, suggesting the open behaviour of the Rb/Sr chronometer in Archean rocks of the PMC.
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