New age determinations for the Banhadão and Itapirapuã complexes in the Ribeira Valley, southern Brazil

AUTOR(ES)

Gomes, Celso de Barros, Azzone, Rogério Guitarrari, Ruberti, Excelso, Vasconcelos, Paulo Marcos de, Sato, Kei, Rojas, Gaston Eduardo Enrich

FONTE

Braz. J. Geol.

DATA DE PUBLICAÇÃO

08/03/2018

RESUMO

ABSTRACT: New age determinations by Ar-Ar and U-Pb SHRIMP for the alkaline complexes of Banhadão and Itapirapuã that occur in the Ribeira Valley are in agreement with the previously radiometric K-Ar ages available in literature. Ar-Ar ages on biotite for Banhadão range in the 106-110 Ma interval, and suggest a minimum age of 106 Ma for the complex. Ar-Ar data on biotite for Itapirapuã are more uniform, indicating an age of 102 Ma for the complex. U-Pb SHRIMP determinations on titanite from Itapirapuã melanite syenitic rocks yielded an age of ~106 Ma. Thus, the age interval of 100 and 110 Ma does exist indeed, suggesting an intermediate magmatic pulse between the already well-defined peaks of 80-90 Ma and 130-140 Ma for the alkaline rocks in southern Brazil, confirming the periodicity of the magmatism.

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