RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 1, NO. 2, PAGES 179–222, doi:10.2205/1999ES000015, 1999
Low mantle plume component in 370 Ma old Kola ultrabasic-alkaline-carbonatite complexes: Evidences from rare gas isotopes and related trace elementsI. N. Tolstikhin, I. L. Kamensky, V. A. Nivin, V. R. Vetrin, E. G. Balaganskaya, S. V. Ikorsky, M. A. Gannibal, and Yu. M. Kirnarsky Geological Institute, Kola Scientific Centre, Russian Academy of Sciences, Apatity, Russia B. Marty Centre National de la Recherche Scientifique Centre de Recherches Petrographiques et Geochimiques(C.R.P.G.), Vandoeuvre-Nancy Cedex, France D. Weiss, A. Verhulst, and D. Demaiffe Petrologie et Geodynamique Chimique Department des Sciences de la Terre et de l`Environnement Faculte des Sciences Universite, Bruxelles, Belgique
 During Devonian pulse of alkaline magmatism (370 Ma ago) 18 ultrabasic-alkaline-carbonatite complexes were formed on the Kola Peninsula. Rare gas isotope abundances were studied in ~300 samples from 8 complexes and also from Devonian dikes. A comparison of expected from in-situ closed-system production (calc) and measured (meas) abundances has shown that 4He meas 4Hecalc whereas in some rocks and minerals 3Hemeas exceeded 3Hecalc up to 1,000 times indicating occurrence of a mantle fluid in a majority of samples. Gas extraction liberated fluid-related helium with as low 4He/3He ratios as 3 x 104. These values show a contribution of 3He-rich plume-like component. A reason for highly variable 4He/3He ratios is not well understood yet. Isotope composition of Ne supports the occurrence of plume component: 20Ne/22Ne ratio varies from 10.4 to 12.0 and 20Ne/22Ne versus 21Ne/22Ne correlation is quite similar to that observed for Loihi hot spot, Hawaii. A comparison of these data with rare gas systematic in the mantle enable us to suggest a contribution of material from the less degassed deep mantle reservoir, source of primordial rare gases, to Devonian ultrabasic-alkaline and carbonatite rocks on the Kola Peninsula.
Received 5 December 1998; published 12 February 1999.
Keywords: mantle plume, rare gas isotopes, trace elements.
Citation: Tolstikhin, I. N., I. L. Kamensky, V. A. Nivin, V. R. Vetrin, E. G. Balaganskaya, S. V. Ikorsky, M. A. Gannibal, Yu. M. Kirnarsky, B. Marty, D. Weiss, A. Verhulst, and D. Demaiffe (1999), Low mantle plume component in 370 Ma old Kola ultrabasic-alkaline-carbonatite complexes: Evidences from rare gas isotopes and related trace elements, Russ. J. Earth Sci., 1, No.2, 179-222, doi:10.2205/1999ES000015. Copyright 1999 by the Russian Journal of Earth Sciences
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