In Deep

Abstract

Multiple regression analysis was used to determine the relative im- portance of crystal fractionation, partial melting, and seawater alteration on the concentrations of 28 elements in deep ocean basalt. The components AI2O3, P2O5, and H2O were used as independent variables to represent each of these processes, and the computer- derived equations show a high level of significance for all 28 elements.The AI2O3, total Fe, and TiCh of oceanic basalt vary greatly in any given region of the oceanic crust due to small-scale crystal settling. The oceanic crust is enriched in large-ion-lithophile (LIL) elements with time by off-ridge volcanism. With the notable exception of Zr and Hf, seawater alteration probably affects the concentration of LIL elements, but much less than partial melting. Seawater altera- tion leaches significant amounts of Si and Ca from oceanic basalt while enriching it in K, Li, and B.