www.elsevier.com/locate/rgg Late Permian and Early Triassic magmatic pulses in the Angara–Taseeva syncline, Southern Siberian Traps and their possible influence on the environment M.T. Paton a , A.V. Ivanov b, * , M.L. Fiorentini a , N.J. McNaughton c , I. Mudrovska a , L.Z. Reznitskii b , E.I. Demonterova b a Centre for Exploration Targeting, School of Earth and Environment, University of Western Australia, 35 Stirling Highway, Crawley 6009, Western Australia, Australia b Institute of the Earth’s Crust, Siberian Branch of Russian Academy of Sciences, Lermontov St. 128, Irkutsk, 664033, Russia c John de Laeter Centre, School of Applied Physics, Curtin University of Technology, Kent Street, Bentley 6102 Western Australia, Australia Received 22 March 2010 Abstract Recently it has been suggested that the major influence on the environment from Siberian Traps magmatism was due to the interaction of magma and organic-rich shale and petroleum-bearing evaporites, with the subsequent creation and outburst of toxic gases (Siberian gas venting: SGV model). In part this idea was supported by a U-Pb age of 252.0 ± 0.4 Ma for one of the dolerite sills in the southeastern Siberian Traps: the age corresponds to the Permo-Triassic boundary and its known mass extinctions of biota. In this study two other dolerite sills were dated using zircons by the U-Pb SHRIMP method at 254.2 ± 2.3 Ma and 249.6 ± 1.5 Ma. The former age is in agreement within error with the age previously published for the dolerite sills, whereas the latter age is in agreement with U-Pb ages published for lava and intrusions from the northern Siberian Traps. The new ages corresponds to the Cahngshingian/Wuchiapingian or Permian/Triassic and Spathian/Smithian boundaries, respectively. Review of 40 Ar/ 39 Ar and U-Pb SHRIMP ages previously published for the southeastern Siberian Traps shows that three other pulses of magmatism probably took place at respectively Anisian/Spathian, Late/Middle Anisian and Landian/Anisian boundaries. Thus it is possible that the SVG model can be applied also to lesser biotic extinctions and recoveries in proximity and aftermath to the main Permo-Triassic extinction. © 2010, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. Keywords: Siberian Traps; U-Pb SHRIMP age Introduction The Late Permian biotic crisis was one of the most sever in the Earth’s history, accounting for the extinction of 90% of marine and 75% of terrestrial species (Erwin, 1994). The main cause of this crisis is generally ascribed to magmatism of the Siberian Traps, mainly on the basis of geochronological and sedimentology/volcanology data (Courtillot and Renne, 2003; Reichow et al., 2008; Renne et al., 1995). However, the direct influence of magmatism on the surrounding (and global) environment is not constrained. Recently, Svensen et al. (2009) suggested that major poisoning took place during magmatism due to interaction of magma and organic-rich shale and petroleum-bearing eva- porites, with the subsequent creation and outburst of toxic gases (Siberian gas venting: SGV model). Svensen et al. (2009) dated zircons by the U-Pb method at 252.0 ± 0.4 Ma from one of the many intrusive sills that were emplaced within petroleum-bearing sediments in the Siberian Traps province (Vasil’ev et al., 2000). The age reported by Svensen et al. (2009) overlaps within error with the U-Pb age of the Permo-Triassic boundary at 252.6 ± 0.2 Ma (Mundil et al., 2004). However, available 40 Ar/ 39 Ar ages for intrusive rocks from regions that are more than 500 km to the south west of the locations where Svensen et al. (2009) carried out their work (cf. Fig. 1) indicate that some sills were emplaced during the Early and Middle Triassic (Ivanov et al., 2005; 2009). Some Triassic 40 Ar/ 39 Ar ages for intrusive rocks were also obtained Russian Geology and Geophysics 51 (2010) 1012–1020 * Corresponding author. E-mail address: aivanov@crust.irk.ru (A.V. Ivanov) doi:10.1016/j.rgg.2010.0 00 1068-7971/$ - see front matter D 2010, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. V S. . Sabolev 8. 9