OPEN CLUSTER CHEMICAL-COMPOSITION .1. LATER TYPE STARS IN 8 CLUSTERS

Abundance analyses of 36 stars associated with eight open clusters (IC 258 1, NGC 3532, NGC 5822, NGC 6067, NGC6087, IC 4725 (M25), IC 4756, and NGC6882/6885) are presented. The stars are primarily evolved G an d K giants and supergiants. Cepheids in NGC 6067, NGC 6087, and IC 472 5 are included as are non-cluster Cepheids near the clusters NGC 3532, NGC 6067, and IC 472 5. With the addition of a background K giant in IC 4725, the total number of stars is 40. Elemental abundances derived include Li, C, N, O, the alpha-elements, the Fe peak, and limited dat a on the heavy elements. The Na abundances of the sample show a gravit y dependence in the sense of an increase in the abundance as the gravi ty decreases. The CNO abundances indicate that these objects are proce ssed (on the whole), and that they show the O deficiency previously no ted in inter-mediate mass stars by Luck & Lambert ( 1981, 1985). There are four stars in the sample which appear to be unprocessed: two gian ts and two supergiants. There are also two super-Li stars in the sampl e, one of which is most likely a weak G-band star. It is suggested tha t the super-Li F supergiants could be evolved blue stragglers. The mos t striking result of the study is the finding that the [O/Na] ratio co rrelates strongly with the gravity and the stellar mass, thus implying that there is a nonstandard additional mixing process affecting the s urface abundances of these stars. A promising candidate for the mixing process is the turbulent diffusive mixing process proposed by Denisse nkov (1993) which brings Na to the surface and which could also lead t o a modification of the oxygen content.