Sills and gas generation in the Siberian Traps

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 100m 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 115130m range and a maximum thickness of 428m. Thermal modelling of the cooling of the sills shows that the contact metamorphic aureoles are capable of generating 5280 tonnes of CO2m2 with contributions from both marine and terrestrial carbon. When up-scaling these borehole results, an area of 1219000km2 is required to generate...