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Zircon U–Pb geochronology from the Paraná bimodal volcanic province support a brief eruptive cycle at ~ 135 Ma

2010; Elsevier BV; Volume: 281; Issue: 1-2 Linguagem: Inglês

10.1016/j.chemgeo.2010.11.031

1872-6836

Víter Magalhães Pinto, Léo Afrâneo Hartmann, João Orestes Schneider Santos, Neal J. McNaughton, Wilson Wildner,

Paleontology and Stratigraphy of Fossils

Ion microprobe U–Pb isotopic data on zircons from the Paraná magmatic province are presented from one tholeiitic (high-Ti Pitanga type) and three felsic volcanic rocks from the low-Ti Palmas and high-Ti Chapecó types. Igneous zircons from the four volcanic rocks yield volcanism ages within error: i.e. 134.4 ± 1.1 Ma (basalt), 134.6 ± 1.4 Ma (rhyodacite), 134.8 ± 1.4 (quartz latite) and 135.6 ± 1.8 Ma (quartz latite). The age of Paraná magmatism based on previous Ar–Ar geochronology has two divergent ranges: 1) 1 to 2 million years with magmatic peak at 131–133 Ma, and 2) over ~ 10 m.y. between 137 and 127 Ma. Our results show that the bimodal volcanics of the province, at least to the south of the Piquiri lineament, have very high effusion rates over a brief period with a main pulse at ~ 135 Ma, about 2% older than proposal 1, more akin to a short period of magmatism. These results are most significant for the understanding of time relations in this large intraplate magmatic province.