LITHIUM, AGE, AND METALLICITY IN OPEN CLUSTERS

It is shown that a strong relationship exists between Li abundance and age for stars in the temperature region 5950-6350 K. The relation is derived from mean Li abundances in eight open clusters ranging in age from 5 x 10(7) to 8 x 10(9) yr. The Li declines exponentially with t-0.3. It is suggested that in this temperature regime that simple microscopic diffusion is the cause of the Li depletion. It is possible that there is a metallicity term in the relation such that higher metallicity clusters with deeper convection zones have less Li depletion, while lower metallicity clusters undergo greater depletion. This is consistent with expectations from diffusion theory. Furthermore, the halo stars, with even lower metallicity and shallower convection zones, would have more diffusion and more Li depletion; this is in agreement with recent theoretical work.