Strontium Isotopes in some Seamount Basalts from the Northeastern Pacific Ocean

Abstract

⁸⁷Sr/⁸⁶Sr 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 K₂O/(K₂O+Na₂O). These basalts seem to be similar to oceanic island basalts in alkali element concentrations, ⁸⁷Sr/⁸⁶Sr and K₂O/(K₂O+Na₂O) 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 ⁸⁷Sr/⁸⁶Sr 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.