Zircon U-Pb geochronology from the Parana bimodal volcanic province support a brief eruptive cycle at ∼135 Ma

Ion microprobe U-Pb isotopic data on zircons from the Parana magmatic province are presented from one tholeiitic (high-Ti Pitanga type) and three felsic volcanic rocks from the low-Ti Palmas and high-Ti Chapeco 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 Parana 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 similar to 10 my. 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 similar to 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. (C) 2010 Elsevier B.V. All rights reserved.