Isotopic ratios of oceanic leads so nearly coincide with those of the youngest ore leads as to suggest sea water as the principal source of ore leads. The connate water buried with marine sediments may deposit its metals within the original host beds, or may migrate under the stimulus of deformation or igneous deposit to form typical epigenetic deposits. Isotopic age of ore lead may conform with that of the host rocks, but is commonly older, or more rarely younger, depending on path of migration. Anomalous leads generally represent contamination by radiogenic lead from Precambrian basement.

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