Analysis evaluates 87Sr/86Sr ratios in basalts, revealing insights on mantle sources in Siberian Platform.
Variations in 87Sr/86Sr ratios are examined in the lava section in two regions of the Siberian Platform: northwest and center of the Tunguska Syneclise. The ratios vary over a wide range from 0.70470 to 0.71027. The highest values are shown to be typical of the lower section, where basalts of higher alkalinity are also recognized. The total enrichment of the Siberian basalts, their low-K varieties included, in incoherent elements and their 87Sr/86Sr ratios higher than in MORB suggest the presence of an enriched source in the mantle of continental lithosphere plates. The nature of this enrichment seems to be connected with ancient buried subduction zones. Regular variations of geochemical and isotope characteristics of basalts in time are, in turn, due to subsequent depletion of the mantle substrate as the magma evolved.
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Almukhamedov et al. (1992) studied this question.
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