Produção Nacional
Zircon U-Pb geochronology, Sm-Nd and Pb-Pb isotope systematics of Ediacaran post-collisional high-silica Acampamento Velho volcanism at the Tupanci area, NW of the Sul-Rio-Grandense Shield, Brazil
2017; Sociedade Brasileira de Geologia; Volume: 47; Issue: 4 Linguagem: Inglês
10.1590/2317-4889201720170064
ISSN2317-4889
AutoresCarlos Augusto Sommer, Felipe Padilha Leitzke, Evandro Fernandes de Lima, Carla Joana Santos Barreto, Jean Michel Lafon, Vinícius Matté, Ruy Paulo Philipp, Rômmulo Vieira Conceição, Miguel Ângelo Stipp Basei,
Tópico(s)Geochemistry and Elemental Analysis
ResumoABSTRACT: We present new U-Pb zircon ages and Sm-Nd-Pb isotopic data for volcanic and hypabyssal acid rocks from the northernmost exposure of the Acampamento Velho Formation in the NW portion of the Sul-Rio-Grandense Shield, Brazil. The first volcanic episode, grouped in the high-Ti rhyolites from the Tupanci hill, shows age of 579 ± 5.6 Ma, which is in agreement with the post-collisional Acampamento Velho Formation volcanism in the Bom Jardim Group of the Camaquã Basin. A poorly constrained age of 558 +/- 39 Ma was obtained for rhyolites from the low-Ti group at the Picados Hill, which may indicate a younger acid volcanism, or a greater time span for the volcanism of the Acampamento Velho Formation in southernmost Brazil. Regarding magmatic sources, Sm/Nd isotopic data coupled to Pb isotopes and a review of trace element geochemistry indicate different amounts of Paleoproterozoic (Dom Feliciano, Pinheiro Machado Suite) to Neoproterozoic (Rio Vacacaí terrane) lower crust melting. Our data, coupled with literature data, contribute to a better understanding of the stratigraphic evolution for the Neoproterozoic post-collisional volcanic successions of the Camaquã Basin in the Sul-Rio-Grandense Shield.
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