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| Titel |
Origin of Siberian Traps and their relation to the Permo-Triassic mass extinction |
| VerfasserIn |
Stephan Sobolev, Alexander Sobolev, Dmitri Kuzmin, Nadezhda Krivolutskaya, Alexey Petrunin, Nick Arndt, Viktor Radko, Yuri Vasiliev |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250049995
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| Zusammenfassung |
| The Large Igneous Provinces (LIPs) are known for their production of up to several million
km3 of magma in less than a few million years. They are likely associated with dramatic
thinning of the lithosphere and they are often related to global environmental catastrophes.
Despite the obvious importance of understanding the origin of LIPs, controversy surrounds
even the basic idea that LIPs form through melting in the heads of thermal mantle plumes.
The classic example of the “origin-problematic” LIP is the Permo-Triassic Siberian Traps, the
largest continental LIP synchronized with the largest known mass-extinction event. It was
erupted at a thick cratonic lithosphere, but there was no lithospheric stretching and
pre-magmatic uplift, expected above the mantle plume head. It is also commonly believed
that CO2 magma degassing from the Siberian Traps was not enough to trigger climatic
crises.
Here we present a numerical finite element thermomechanical model and supporting
petrological data implying a large amount (ca. 15 Wt%) of recycled oceanic crust within the
head of a hot mantle plume beneath the cratonic lithosphere. Model and data suggest that the
Siberian Traps originated from the melting of the head of a mantle plume with a potential
temperature of about 1600C, that contained about as much dense recycled oceanic crust as it
could carry, thus maintaining almost neutral buoyancy in the mantle. Because of the low
buoyancy of the plume, no pre-magmatic uplift was produced. The large amount of melt
generated from this plume was responsible for the heterogeneous delamination of
the thick cratonic lithosphere over a few hundred thousand years. Degassing of
CO2 and HCl stored in the recycled crust within the plume was likely much more
extensive than previously proposed. The predicted quantity of released CO2 (120-150
1012 tones) and isotopic composition of C (δ13C=-12 promille) is consistent with
data on isotopic excursions for C and Ca at Permo-Triassic boundary (Payne et al.,
PNAS, 2010) and was probably enough to trigger the Permo-Triassic mass-extinction
event.
According to our model, the main mass extinction event must have happened before the
main phase of flood basalt extrusion. In contrast, the CO2 from the heating of carbon-rich
sediments that was recently suggested as a trigger for the mass extinction (Ganino and Arndt,
Geology, 2009; Svenson et al., EPSL, 2009) should be released during the main
phase of magmatism, when the largest magmatic heat input is expected. The new
precise U/Pb dating of the magmatic units of the Siberian traps is required to choose
between these two hypotheses. However, the existing few high-quality U/Pb datings
(Kamo et al., EPSL, 2003; Svenson et al., EPSL, 2009) indeed suggest that the major
mass-extinction event at 252.3 Ma (Mundil et al., GS London SP, 2010) predated the
main phase of magmatism, that may be common for other LIPs as well (Wignall,
ES Rev.,2001). Additional large amounts of gases released from the heating of
coal-rich sediments during the main phase of the Siberian Traps may have been the
reason for a number of C excursion pulses during the late phases of the biotic crises. |
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