Data/hora: 01/06/2024 06:09:53

Provedor de dados: | 42
País: | Brazil
Título: | 40Ar/39Ar ages (600-570 Ma) of the Serra do Azeite transtensional shear zone: evidence for syncontractional extension in the Cajati area, southern Ribeira belt
Autores: | Machado,Rômulo; Dehler,Nolan M.; Vasconcelos,Paulo.
Data: | 2007-12-01
Ano: | 2007
Palavras-chave: | Syncontractional extension; 40Ar/39Ar ages; Ribeira belt.
Resumo: | This paper presents 40Ar/39Ar ages of the rocks from the Serra do Azeite transtensional shear zone in the southern part of the Ribeira belt, between the States of São Paulo and Paraná, and also discusses the regional correlations and the tectonic implications for other parts of the belt. The geochronological data suggest that transtensional deformation was active between 600 and 580 Ma (hornblende and muscovite apparent ages, respectively). This time span is considerably older than previous proposals for the period of activity of these structures (520-480 Ma) in the northern segment of this belt and in the Araçuaí belt. Kinematic analysis of the dated mylonites shows extensional structures with top-down movement to ESE compatible with structures found in other tectonic segments in the eastern portion of the Quadrilátero Ferrífero and in the Rio Doce Valley region. Our ages are situated in the same time interval defined for the alkaline magmatism of the Serra do Mar suite. We suggest that the regional tectonic framework was developed during continental-scale extension. This process has been coeval with convergent strain in the adjacent Neoproterozoic shear zones of the Apiaí/Ribeira and Araçuaí belts, which make up significant segments of these belts. The available data show that these structures may not be simply related to post-orogenic gravitational collapse, but must involve a more complex process probably related to dynamic balance between crustal thickening and thinning during tectonic convergence, basin formation and exhumation processes.
Tipo: | Info:eu-repo/semantics/article
Idioma: | Inglês
Identificador: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000400011
Editor: | Academia Brasileira de Ciências
Relação: | 10.1590/S0001-37652007000400011
Formato: | text/html
Fonte: | Anais da Academia Brasileira de Ciências  v.79 n.4 2007
Fonte: | info:eu-repo/semantics/openAccess