Strontium Isotopes in some Seamount Basalts from the Northeastern Pacific Ocean

<SUP>87</SUP>Sr/<SUP>86</SUP>Sr ratios in seven seamount basalts from the northeastern Pacific Ocean range from 0.7022 to 0.7034 and correlate significantly with chemical composition as expressed by the ratio K<SUB>2</SUB>O/(K<SUB>2</SUB>O+Na<SUB>2</SUB>O). These basalts seem to be similar to oceanic island basalts in alkali element concentrations, <SUP>87</SUP>Sr/<SUP>86</SUP>Sr and K<SUB>2</SUB>O/(K<SUB>2</SUB>O+Na<SUB>2</SUB>O) ratios suggesting similar mantle source materials, possibly least depleted in dispersed elements. However, in places, seamount basalts also appear to resemble ridge tholeiites. Large differences in <SUP>87</SUP>Sr/<SUP>86</SUP>Sr and Rb/Sr ratios for the samples from the Cobb seamount appear to indicate isotopic variations in the source materials, perhaps resulting in the formation of different lava flows within the seamount