Comparative characteristics of Middle Paleozoic and Late Riphean plume magmatism of the Siberian platform |
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| Authors: | A I Kiselev V V Yarmolyuk I I Kolodeznikov |
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| Institution: | 1.Institute of the Earth’s Crust, Siberian Branch,Russian Academy of Sciences,Irkutsk,Russia;2.Institute of Geology of Ore Deposits, Petrography, Minerology, and Geochemistry,Russian Academy of Sciences,Moscow,Russia;3.Yakutsk State University,Yakutsk,Russia |
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| Abstract: | Based on isotopic and geochemical data for Late Riphean dikes and sills and for Devonian dolerite dikes and basalt covers
within the Sette-Daban rift in the western part of the Siberian platform, we proved conceptions about the participation of
various deep sources in their formation. The inverse correlation in Devonian basites between concentrations of Nb, light rare
earth elements, and a number of other highly incompatible elements on the one hand and Zr, Y, and other moderate incompatible
elements, including heavy rare earth elements on the other hand allows us to assume that two sources participated in the formation
of melts. The source of dolerites is close to the EMORB type, and the source of basalts is close to the OIB type. The compositions
of Riphean rocks correspond to a trend for which magma formation occurred with the participation of a source with characteristics
between NMORB and EMORB and also a component typical of subduction zones. The data obtained imply associate formation of basites
with the influence of mantle plumes on the lithosphere of the southeastern part of the Siberian craton in the Late Riphean
and Middle Paleozoic. In the Riphean the plume mantle was composed of a moderately depleted mantle of the EMODB type and a
mantle with the composition close to the above-subduction mantle, which was metosomatically changed under the influence of
fluid water, which caused the appearance of a Nb and Ta deficit in melting products. The isotopic characteristics Nd(147Sm/144Nd = 0.165 and ɛNd(T) ∼ 2.3–4.7) of rocks show the moderate depleted nature of these sources. |
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