Volatilized lead from Apollo 12 and 14 soils.

Lead in some Apollo-12 and -14 soils and breccias was volatilized under vacuum at temperature intervals of 0 to 600 C, 600 to 800 C, 800 to 1000 C, and 1000 to 1350 C. It is found that the Pb(206)/Pb(204) ratio increases and the Pb(207)/Pb(206) ratio decreases in the temperature range between 600 and 1000 C. The Pb(208)/Pb(206) ratios decrease from a value of 2 at 600 C to a value of 0.7 at 1350 C. These and other data suggest a secondary isochron age of about 4200 million years.