Several barites from the lead-barite district contain between 1,170 and 1,633 ppm Sr. Their 87 Sr/ 86 Sr ratios range from 0.7098 to 0.7118, in contrast to the values of 0.7082 to 0.7089 for the host carbonate rocks. Four galenas from the Viburnum Mine in Southeast Missouri provide a Rb-Sr age of 392 + or - 21 m.y. and an initial isotopic composition of 0.7104 + or - 0.0004, indicating the period of mineralization to be Early Devonian.--Modified journal abstract.

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