Behaviour of rare earth elements during submarine weathering of tholeiitic basalt

DREDGED oceanic basalts and those sampled by deep-ocean drilling have commonly undergone some weathering with subsequent changes in their chemical composition^1-7. The rare-earth elements (REE) La-Lu are generally considered to be unaffected by weathering and are thus often used to characterise variations in basalt and magma composition. When considered relative to chondritic abundances⁸, the overall REE distribution is a critical diagnostic tool. In particular, the relative depletion of light-REE is used to discriminate between magma types. We present here new findings which show that REE are affected by low-temperature weathering processes. In particular, the light-REE show enrichments which may result in a basalt with a primary light-REE depleted pattern showing a flat or enriched light-REE pattern.