Lead Age Measurements on Galenas from Peninsular India

Measurements of lead isotope ratios on some Indian galenas and calculation of single-stage model ages were presented in a previous paper. Techniques have been improved since then, and more samples from some of these areas and several new samples have been measured. The present measurements cover a wide age-span, Eocene to Archaean (∼3300 m.y.) and the Pb-isotope abundances are not inconsistent with a 2-stage evolution of lead which show an episodic change in μ-value at ∼ 3000m.y. Model ages and μ-values have been calculated using single and double-stage models and an attempt made to interpret these values.