Strontium isotope and alkali element geochemistry of selected sediments from the northeast Pacific Ocean
Few chemical and isotopic data exist for bulk samples of ocean basin clays. Such data are necessary to evaluate subduction models for the genesis of calc-alkaline rocks. The northeast Pacific Ocean provides a locale in which one can evaluate the possible chemical effects of both oceanic volcanism and continental sedimentation on ocean basin sediments. Sr 87/Sr 86 ratios for these bulk sediment samples vary with the concentration of strontium and range from values near that of marine strontium to more radiogenic values (0.7081-0.7165). Potassium and rubidium concentration data indicate a rather constant K/Rb ratio ranging from 350 to 440 with one exception. Variable Rb/Sr ratios reflect a mixed mineralogy, also indicated by X-ray diffraction data. Various mixtures of detrital minerals, dominately clays, and carbonate minerals logically explain the variation of the strontium data.