Moon, and Tektites

Sample Handling. Most papers devote little attention to sample handling prior to lead extraction and purification. Lead contamination is particularly likely in most rock-lead work because of the widespread use of white lead house paint and the fallout of lead tetramethyl aerosols from gasoline. Great care must be taken to avoid contamination. 

Method of Lead Isolation. Some satisfactory and commonly used methods of lead isolation were given in Table 2. 

Methods of Abundance Measurement. Mass spectrometry (Table 2) is the common form of analysis for lead isotope abundances. Samples suitable for mass spectrometer calibration are in Table 3. Neutron activation ( ° Pb/ ° Pb) and alpha particle activation ( ° Pb/ Pb and ° Pb/ ° Pb) show promise of getting some data on materials having very low lead contents. 

Studies of lead isotopes in meteorites have been very fundamental to all of earth science the first reliable age of meteorites was a lead isochron age (Patterson, 1955), and the accepted age of the earth stems from meteorite studies (Patterson, 1953 Patterson et al., 1955). 

The isotopic composition of lead in some meteorites is given in Table 13 and plotted in Fig. 12. The selection of meteorites is taken from the evaluation of Murthy and Patterson (1962). Also given are the newly recommended values determined by Oversby (1970) where the ratios have been corrected for mass spectrometer bias, and the attempt has been made to eliminate samples that have suffered terrestrial lead contamination. Stacey et al. (1969) have pointed out that there is little change in derived values such as age of the earth or primary 2 8u/204pb if all samples are in absolute ratios. Care should therefore be taken to make sure that all samples are in absolute ratios when using the values of primordial lead recommended by Oversby (1970). Other papers of interest are by Starik et al. (1962a), Sobotovich et al. (1964), and Marshall (1968). 

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