Sills and gas generation in the Siberian Traps

• Published in: Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences physical, and engineering sciences, 2018-10, Vol.376 (2130), p.20170080
• Main Authors: Svensen, Henrik H., Frolov, Sergei, Akhmanov, Grigorii G., Polozov, Alexander G., Jerram, Dougal A., Shiganova, Olga V., Melnikov, Nikolay V., Iyer, Karthik, Planke, Sverre
• Format: Article
• Language: English
• Subjects: End-Permian; Large Igneous Provinces; Siberian Traps
• ISSN: 1364-503X; 1471-2962
• DOI: 10.1098/rsta.2017.0080

On its way to the surface, the Siberian Traps magma created a complex sub-volcanic plumbing system. This resulted in a large-scale sill emplacement within the Tunguska Basin and subsequent release of sediment-derived volatiles during contact metamorphism. The distribution of sills and the released sediment-stored gas volume is, however, poorly constrained. In this paper, results from a study of nearly 300 deep boreholes intersecting sills are presented. The results show that sills with thicknesses above 100 m are abundant throughout the upper part of the sedimentary succession. A high proportion of the sills was emplaced within the Cambrian evaporites with average thicknesses in the 115-130 m range and a maximum thickness of 428 m. Thermal modelling of the cooling of the sills shows that the contact metamorphic aureoles are capable of generating 52-80 tonnes of CO2 m−2 with contributions from both marine and terrestrial carbon. When up-scaling these borehole results, an area of 12-19 000 km2 is required to generate 1000 Gt CO2. This represents only 0.7-1.2% of the total area in the Tunguska Basin affected by sills, emphasizing the importance of metamorphic gas generation in the Siberian Traps. These results strengthen the hypothesis of a sub-volcanic trigger and driver for the environmental perturbations during the End-Permian crisis. This article is part of a discussion meeting issue 'Hyperthermals: rapid and extreme global warming in our geological past'.