“Common lead” is any lead from a phase with a low value of U/Pb and/or Th/Pb such that no significant radiogenic lead has been generated in situ since the phase formed. Such phases are galena and other sulfides such as pyrite, feldspars and in particular K-feldspar, micas, and most abundant rock types of Cenozoic age. Data on common lead are used in determining ages and, more important, in the Solution of genetic problems. Presented herein, therefore, are data on those phases relevant to common lead applications even if sufficient radiogenic lead has been generated to markedly alter the initial isotopic composition of the lead such as in Precambrian crystalline rocks.
KeywordsIsotopic Composition Igneous Rock Lead Isotope Baltic Shield Manganese Nodule
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