USING U/PB GEOCHRONOLOGY TO DETERMINE THE TIMING AND TEMPO OF THE SIBERIAN TRAPS LARGE IGNEOUS PROVINCE MAGMATISM

Large igneous province magmatism is characterized by rapid (ca. 1 Ma) eruption and intrusion of large (>10⁶ km³) volumes of magma into and onto Earth’s crust. Broad interest in the timing and duration of LIP magmatism stems from (1) the potential role of voluminous magmatism as a trigger for catastrophic environmental change and mass extinction, and (2) the geodynamic and petrologic implications of rapidly generating, emplacing, and erupting >10⁶ km³ of magma. For example, the Siberian Traps LIP, which represents the largest volume continental magmatic event in the Phanerozoic, was relatively rapidly erupted/emplaced onto stable cratonic lithosphere and has been widely implicated as the primary trigger for the most severe Phanerozoic mass extinction, the end-Permian. There is considerable debate over how such large volumes of magma were generated on short timescales and how LIP magmatism may be linked to the end-Permian biotic crisis. Detailed models aimed at assessing the mechanisms by which magmas are generated and erupted and how they may affect the biosphere are hampered by a lack of high-precision (< 0.1%) geochronology. Improved understanding of the origin of LIPs and their potential role in triggering global environmental change requires temporal control with uncertainty that is on the order of, or even smaller than the timescale over which magmatism occurred.

To accurately and precisely define the timing and tempo of intrusive and extrusive magmatism of the Siberian Traps LIP, we use high-precision U/Pb ID-TIMS geochronology of single zircon and perovskite crystals from pyroclastic rocks, lavas, and sills from throughout the magmatic province. From these data we conclude: (1) Pyroclastic eruption and a significant volume of lava eruption began prior to the onset of the end-Permian mass extinction. (2) Lava eruption and intrusion continued through the mass extinction interval, into the early Triassic. (3) The total duration of magmatism is in excess of 1 Ma but most of the LIP was erupted/emplaced in < 600 kyr. Our new age model permits, for the first time, a detailed evaluation of the Siberian Traps LIP eruption/emplacement tempo and duration that can be compared with other LIPs, and allows speculation as to why the Siberian LIP had such devastating environmental consequences.