pb–pb isochrons oldest known material in solar system. chondrules , calcium–aluminium-rich inclusions (cais) spherical particles make chondritic meteorites , believed oldest objects in solar system. hence precise dating of these objects important constrain evolution of solar system , age of earth. u–pb dating method can yield precise ages solar-system objects due optimal half-life of u. however, absence of zircon or other uranium-rich minerals in chondrites, , presence of initial non-radiogenic pb (common pb), rules out direct use of u-pb concordia method. therefore, precise dating method these meteorites pb–pb method, allows correction common pb. when abundance of pb relatively low, isotope has larger measurement errors other pb isotopes, leading strong correlation of errors between measured ratios. makes difficult determine analytical uncertainty on age. avoid problem, researchers developed ‘alternative pb–pb isochron diagram’ (see figure) reduced error correlation between measured r...
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