Genetic implications of the isotope and trace element variations in the eastern Sicilian volcanics |
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| Authors: | SR Carter L Civetta |
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| Institution: | Department of Geology and Mineralogy, University of Oxford, Oxford ,Great Britain;Istituto di Geologia e Geofisica, Universita di Napoli, Naples ,Italy |
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| Abstract: | Sr- and Pb-isotope compositions and Rb, Sr, Ce, Nd and K2O contents have been determined for the Iblean Mountain and Mt. Etna volcanics in eastern Sicily. Isotope variations within each of these regions have been interpreted as reflecting the heterogeneous nature of the source regions in the upper mantle. The87Sr/86Sr ratios of all these volcanics are less than 0.705, which is taken to indicate that their source regions evolved with lower Rb/Sr ratios than the bulk earth.87Sr/86Sr and Ce/Nd ratios determined in the Mt. Etna tholeiites are positively correlated suggesting that fractionation(s) in Rb/Sr are accompanied by fractionation(s) in light REE in the source regions of these volcanics. Pb-isotope compositions form a linear array in the207Pb/204Pb-206Pb/204Pb plot which has a negative age slope. This array represents either a very recent U/Pb fractionation in the source regions, or a mantle mixing line. Imperfect correlation between the Sr- and Pb-isotope compositions of these volcanics suggests that U/Pb and Rb/Sr have not always increased or decreased in unison during the differentiation of these source regions. |
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