- Siberian Traps
The Siberian Traps ( _ru. Сибирские траппы) form a
large igneous provincein Siberia. The massive eruptive event spans the Permian- Triassicboundary, about 251 to 250 million years ago, and was essentially coincident with the Permian-Triassic extinction eventin what was one of the largest known volcanicevents 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.
Vast volumes of
basaltic lavapaved over a large expanse of primeval Siberia in a flood basaltevent. 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.
Reason for formation
The source of the Siberian Traps basalt is considered to be a
mantle plumewhich impacted the base of the crust and erupted through the Siberian Craton. Helium isotope geochemistryfrom the basalts indicates a plume origin. The scientific debate continues, however. [Czamanske, Gerald K.; Fedorenko, Valeri A. " [http://www.mantleplumes.org/Siberia.html The Demise of the Siberian Plume] ", January 2004.] The other common theory is that the traps were caused by a very large asteroid impact.
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
Norilskin Siberia. Individual eruptions of basalt lavas could have exceeded 2000 km3 or even more. The giant Norilsk-Talnakh nickel- copper- palladiumdeposit formed within the magma conduits in the main part of the Siberian Traps. The presence of extensive tuffand pyroclastic deposits suggests that a number of large explosive eruptions occurred during or before the eruptions of basaltic lavas. The presence of silicicvolcanic rocks such as rhyoliteis also indicative of explosive eruptions.
* [http://palaeo.gly.bris.ac.uk/Palaeofiles/Permian/SiberianTraps.html The Siberian Traps]
* [http://www.ucmp.berkeley.edu/education/events/cowen2a.html The Siberian Traps] , by Richard Cowen
* [http://www.le.ac.uk/gl/ads/SiberianTraps/Index.html The Siberian Traps Large Igneous Province]
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