LATE PERMIAN AND EARLY TRIASSIC MAGMATIC PULSES IN THE ANGARA-TASEEVA SYNCLINE, SOUTHERN SIBERIAN TRAPS AND THEIR POSSIBLE INFLUENCE ON THE ENVIRONMENT
M.T. Patona, A.V. Ivanovb, M.L. Fiorentinia, N.J. McNaughtonc, I. Mudrovskaa, L.Z. Reznitskiib, and E.I. Demonterovab
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
Keywords: Siberian Traps, U-Pb SHRIMP age
Pages: 1012-1020
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 correspond to the Cahngshingian/Wuchiapingian or Permian/Triassic and Spathian/Smithian boundaries, respectively. Review of 40Ar/39Ar and U-Pb SHRIMP ages previously published for the southeastern Siberian Traps shows that three other pulses of magmatism probably took place at Anisian/Spathian, Late/Middle Anisian, and Landian/Anisian boundaries, respectively. 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.
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