HR: 1330h
AN: V12B-0571    [PDF]
TI: Plume or no Plume, the Case of the Siberian Trap Formation
AU: * Reichow, M K
EM: mkr6@le.ac.uk
AF: University of Leicester, Department of Geology, University Road, Leicester, LE1 7RH United Kingdom
AU: Saunders, A D
EM: ads@le.c.uk
AF: University of Leicester, Department of Geology, University Road, Leicester, LE1 7RH United Kingdom
AU: White, R V
EM: rvw1@le.ac.uk
AF: University of Leicester, Department of Geology, University Road, Leicester, LE1 7RH United Kingdom
AU: Al'Mukhamedov, A I
EM: amedv@igc.irk.ru
AF: Institute of Geochemistry, Favorsky Street, 664033 Irkutsk, PO Box 401 Russian Federation
AU: Medvedev, A I
EM: amedv@igc.irk.ru
AF: Institute of Geochemistry, Favorsky Street, 664033 Irkutsk, PO Box 401 Russian Federation
AU: Inger, S
AF: CASP, University of Cambridge, West Building, Gravel Hill, Huntingdon Road, Cambridge, CB3 0DJ United Kingdom
AB: The generation mechanism of continental large igneous provinces, such as the Siberian Traps, are matters of recent debate, particularly their relation to mantle plumes derived from the Earth's interior. Alternative models relate the formation of large igneous provinces to bolide impacts or small-scale convection at the boundary of asymmetric lithospheres. Neither of these models is without criticism and each model cannot explain all characteristics of continental flood basalt formation alone. However, strong support for the involvement of a mantle plume comes from the observation that large volumes of basaltic melts ($\sim$3 x 10$^{6}$ km$^{3}$) erupted within a short period of time ($<$ 1 My). Such high magma flux rates can only realistically be produced by decompression melting in the head of an uprising mantle plume. Although several areas surrounding the Siberian craton have been attributed to the Siberian Traps volcanic activity, the entire extent remains conjectural. Basaltic and gabbroic rocks occur throughout the West Siberian Basin (WSB) beneath a thick succession of Mesozoic and Cenozoic sediments. Further to the north of the Siberian craton, on the Taimyr Peninsula, are also basalt and dolerite rocks. We have obtained more than 100 samples from both areas and compared chemical data with data from the Siberian Traps. The basalts have chemical characteristics typical of fractionated, contaminated continental flood basalts (e.g. low Mg\#, negative Nb anomaly). Trace element modelling suggests that the basalts represent different degrees of partial melting and crustal contamination. The major and trace element data from the WSB and Taimyr basalts show strong affinities with Siberian Trap basalts that precede the main pulse of volcanism extruded over large areas of the Siberian craton. Although the major and trace element data are consistent with a plume origin for the Siberian Traps, they cannot prove it; however, magma volume and timing constraints do strongly suggest that a mantle plume was involved in the formation of the Earth's largest continental flood basalt province.
DE: 0370 Volcanic effects (8409)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting