The Permian-Triassic extinction. A massive intrusion of basaltic magma into the The Tunguska Basin that also created the Siberian Traps. The intrusion heated

The Permian-Triassic extinction. A massive intrusion of basaltic magma into the The Tunguska Basin that also created the Siberian Traps. The intrusion heated organic-rich sediments and evaporites (salt, anhydrite) and caused eruption of gases. Siberia is littered with enormous pipes as much as 1 km in diameter that erupted massive amounts of gas during the event. In addition to CO2 and methane, the gas was loaded with chlorinated hydrocarbons from the salt, which could have devastated the ozone layer. I've seen an estimate that CO2 concentrations in the atmosphere may have reached as high as 30,000 ppm (3%). It was bad luck for the Paleozoic world that this massive mantle plume came up in perhaps the worst possible place. Some of these pipes became filled with magnetite and as a result are mined for this rich iron ore.