Geochemical specifics of massifs of the drusite complex in the central Belomorian Mobile Belt: II. Sm-Nd isotopic system of the rocks and the U-Pb isotopic system of zircons |
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| Authors: | N A Krivolutskaya B V Belyatsky V F Smolkin V P Mamontov A S Fanygin N M Svirskaya |
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| Institution: | 1.Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKhI),Russian Academy of Sciences,Moscow,Russia;2.All-Russia Research Institute of Geology and Mineral Resources of the World Ocean (VNIIOkeanologiya),St. Petersburg,Russia;3.Vernadsky State Geological Museum,Russian Academy of Sciences,Moscow,Russia;4.Murmansk Geological Exploration OJSC,Apatity,Russia |
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| Abstract: | First isotopic-geochemical data were obtained on basite-ultrabasite rocks from the southern Kovdor area that were previously
provisionally ascribed to the drusite (coronite) complex based on the occurrence of drusite (coronite) textures. The mineral
and whole-rock Sm-Nd isochron age determined for five rock samples from the Sorkajoki and Poioiva massifs and the massif of
Elevation 403 m turned out to be close (within the error): 2485 ± 51, 2509 ± 93, and 2517 ± 75 Ma, respectively. The crystallization
age was evaluated for the two massifs (Poiojovski and Mount Krutaya Vostochnaya) by the U-Pb system of zircons. Our samples
contained both magmatic and xenogenic crustal zircons, whose age was estimated at 2700 Ma. The crystallization age of the
massifs themselves (data on the magmatic zircons) is 2410 ± 10 Ma. The undepleted character of the mantle source (ɛNd = +0.9)
and the much younger age of the massifs than that of other known manifestations of ultrabasic magmatism in the territory of
Karelia and the Kola Peninsula (including the layered pluton classic drusite massifs) suggest that the central part of the
Belomorian Mobile Belt hosts one more independent intrusive rock complex, which has never been recognized previously and which
is different from typical drusites. |
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