Quantitative assessment of chemical and mineralogical changes due to progressive low-temperature alteration of East Pacific Rise basalts from 0 to 9 Ma

A comparison of trace element analyses from altered whole rock samples and their appendant fresh glass chips provides a record of element mobility during alteration. Off-axis basalts show significant uptakes of Rb, Cs and Ba which are supplied by seawater and incorporated in or on secondary minerals. An enrichment of U is also apparent and appears to be especially strong when alteration conditions are oxidative. K2O is also gained in all altered off-axis basalts, believed to be linked to the formation of celadonite. However, the volume of rock being altered is so small relative to the volume of the oceans that this scavenging has no noticeable effect on the composition of the oceans. The composition of the oceanic crust, on the other hand, is affected significantly.