Lead isotopic studies from the Austinville-Ivanhoe district of southwest Virginia demonstrate that galenas of different generation have distinct lead isotopic compositions. Within a single orebody paragenetically early galenas have lower lead isotopic ratios than later galenas. In addition, smaller orebodies characteristically show a more radiogenic isotopic signature than larger ore lenses. Mixing of lead from the enclosing sedimentary sequence and basement rocks is suggested as a possible mechanism of generating the isotopic composition of lead near Austinville. Accordingly, the slope of a regression line is thought to have no age significance.
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Foley et al. (1981) studied this question.