Preliminary Interpretations of Lead Isotopes

نویسندگان

  • C. I. Godwin
  • A.
  • Sinclair
چکیده

Large stratiform, syngenetic deposits commonly yield galena-lead isotope 'model' ages that agree closely with the stratigraphic ages of their host rocks. However, analyses in Table 1 from stratiform,shale-hosted deposits (located on Fig. 701 of Cambrian to Devono-Mississippian age in or adjacent to the Selwyn Bar,in in British Columbia and Yukon Territory do not give reasonable ages if the models of Stacey and Kramers (1975) or Cumming and Richards (19751 are used. In fact, ages calculated with these models are unrealistically young, although isotopic analyses from the British Columbia and Yukon Territory deposits, plotted on a 207Pbi204Pb versus 206Pb/2004Pb graph form dirtinctclusters (Fig.71). Each clustercan be characterized by a specific deposit age and the locations of the clusters are in an appropriate order and position to define a growth curve (Fig. 70). The four clusters identified on Figure 71 are:

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تاریخ انتشار 2002