Siberian Traps

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The Siberian Traps (Russian: Сибирские траппы) form a large igneous province in Siberia. The massive eruptive event spans the Permian-Triassic boundary, about 251 to 250 million years ago, and was essentially coincident with the Permian-Triassic extinction event in what was one of the largest known volcanic events of the last 500 million years of Earth's geological history. The term 'traps' is derived from the Swedish word for stairs (trappa, or sometimes trapp), referring to the step-like hills forming the landscape of the region.

1 Geographical extent
2 Reason for formation
3 Siberian Traps and nickel
4 See also
5 References
6 External links

[edit] Geographical extent

Vast volumes of basaltic lava paved over a large expanse of primeval Siberia in a flood basalt event. Today the area covered is about 2 million km² and estimates of the original coverage are as high as 7 million km². The original volume of lava is estimated to range from 1 to 4 million km³.

The area covered lies between 50 and 75 degrees north latitude and 60 to 120 degrees east longitude. The volcanism continued for a million years and spanned the Permian-Triassic boundary. There is no firm evidence that this event caused (or helped cause) the Permian-Triassic extinction event, but the timing of the two events is suggestive of a causal link.

[edit] Reason for formation

The source of the Siberian Traps basalt is considered to be a mantle plume which impacted the base of the crust and erupted through the Siberian Craton. Helium isotope geochemistry from the basalts indicates a plume origin. The scientific debate continues, however.^[1] The other common theory is that the traps were caused by a very large asteroid impact.

[edit] Siberian Traps and nickel

The Siberian Traps are considered to have erupted via numerous vents over a period of roughly a million years or more, probably east and south of Norilsk in Siberia. Individual eruptions of basalt lavas could have exceeded 2000 km³ or even more. The giant Norilsk-Talnakh nickel-copper-palladium deposit formed within the magma conduits in the main part of the Siberian Traps. The presence of extensive tuff and pyroclastic deposits suggests that a number of large explosive eruptions occurred during or before the eruptions of basaltic lavas. The presence of silicic volcanic rocks such as rhyolite is also indicative of explosive eruptions.