The structure and processes of the Siberian Traps sub-volcanic complex and consequences for end-Permian environmental crisis

The emplacement of the Siberian Traps Large igneous province is regarded as the key processes that initiated the end-Permian environmental crisis. The details of this link are however still under investigation. Among the suggestions are lava degassing of mantle- and crustal-derived gases, explosive lava and phreatomagmatic eruptions, and gas release from contact metamorphism related to the sub-volcanic sill complex. Whereas the lava pile is relatively well studied and investigated, the sub-volcanic sills, dikes, and contact aureoles are poorly studied and documented. We present borehole and field data of sills and contact aureoles from across the Siberian Traps, from Norilsk in the north to Bratsk in the south. The data have been compiled during three field campaigns in 2004, 2006, and 2010. The sill geometries and thicknesses varies considerably from kilometer-scale intrusive complexes to individual thin sills of a few tens of meters. In contrast to several other LIPs, sills are also emplaced within the extrusive pile. Thick sills (30-80 meters) occur in high abundance in the upper part of the sedimentary succession, affecting the coal-rich Tungusska Series sediments. Moreover, very thick sills (100-300 meters) are also emplaced within the vast Cambrian salt formations. We show that depending on the specific location within the province and the emplacement depth, the potential for degassing of both greenhouse gases (CH4, CO2), aerosols (SO2), and ozone destructive gases (CH3Cl, CH3Br) was in the 103 to 104 Gt range.