Replicate potassium was measured using LiBO2 flux fusion and flame phtometry with a lithium internal standard. Mineral standards were used to calibrate the photometer. Argon isotopes were measured by isotope dilution on a computerized, 6-in.-radius mass spectrometer. Modifications of analytical techniques are; (1) Reducing air-argon contamination from the extraction system by replacing quartz-lined, air cooled fusion bottles with water-cooled, unlined bottles. (2) Boiling whole-rock samples (crushed to 16-48 mesh) for 1 hr. in distilled water immediately before loading them in the extraction system. (3) Argon from one sample fusion is split into two to four aliquits that are sequentially analyzed on the mass spectrometer. The first [...]