The concentration of the extralunar component in mature Apollo-16 soils is about 3.8%, substantially higher than values observed at Apollo-14 (2.7%) or mare landing sites (1.2-1.3%). It appears that a large amount of local pre-Imbrium regolith was incorporated into Apollo-16 soils: the amount incorporated into Apollo-14 soils was smaller, probably as a result of the combination of two factors: (1) a larger dilution by subregolith materials, and(2) a lower concentration of siderophiles in the ancient Fra Mauro regolith relative to that of the Southern Highlands. Volatiles, siderophiles and cosmogenic isotopes are intercorrelated in Apollo-16 soils, mainly as a result of mixing of mature soils having high concentrations with North Ray Crater ejecta having low concentrations. The distributions of Zn, Cd and In in soils and soil breccias are largely controlled by volatility; a positive correlation with Zn suggests that volatility also affects the distribution of Ga. The concentrations of Zn, Ga and Cd are higher and those of Sc and Fe lower in light relative to dark mature and submature soils. Volatile concentrations appear to be slightly higher in Apollo-14 soils than in Apollo-16 soils.