initial strontium ratio

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initial strontium ratio(common strontium) The ratio between the radioactively produced isotope 87Sr and the ‘ordinary’, non-radiogenic isotope 86Sr at the time when a rock crystallized. 87Sr is produced by the decay of 87Rb and measurements of the present proportions of rubidium and the two strontium isotopes can be used to calculate the initial strontium ratio and the age of the rock. This provides the basis for one of the most important geochronological methods.

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