Strontium isotope studies on young volcanic rocks from Germany and Italy

⁸⁷Sr/⁸⁶Sr ratios of Tertiary tholeiitic, basalts alkali olivine basalts and olivine nephelinites from Lower Saxony and Hessia and Quaternary leucite-nepheline tephrites from the Laacher See area are similar to those obtained from Hawaii and range from 0.7031 to 0.7054. Three trachytes and one phonolite from the Westerwald and one phonolite from the Laacher See area have higher values (0.7063 to 0.7093). Three Vesuvian lavas, three Somma lavas and two trachytes of the Phlegraic Fields show substantially higher ratios than the comparable basaltic rocks from N.W. Germany (0.7071 to 0.7102). Three peridotite nodules vary between 0.7048 and 0.7081. Three limestone composites of Paleozoic and Mesozoic age show values between 0.7129 and 0.7174.The ⁸⁷Sr/⁸⁶Sr ratios of the trachytes and phonolites from the Westerwald and Laacher See area are probably influenced by crustal material. Assimilation processes of limestones producing the olivine-nephelinites from N.W. Germany seem to be unlikely. A discussion of the origin of the Sr ratios in Vesuvian rocks and of mantle homogeneity is included.