Thirteen samples of basaltic rock from the islands of Upolu and Savai'i, Western Samoa, were analyzed for major element composition, for the minor elements Rb, Sr, and Ni, and for strontium isotopic composition. Ten high-potassium alkali basalts and three relatively potassium-rich olivine tholeiites have initial Sr87/Sr86 ratios of from 0.7051 to 0.7066. These values are among the highest yet found from within the ocean basins. The high potash contents and high Sr87/Sr86 ratios suggest that the mantle source material from which these rocks were derived has been less depleted by previous magmatism than much of the suboceanic mantle.

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