ANOTHER LOOK AT RARE-EARTH ELEMENTS IN SHALES

Linear correlation and mass balance considerations indicate that clays are more important than zircon (or other heavy minerals) in hosting both light and heavy REE in cratonic shales. Considering the uniformity of the Eu anomaly and REE distributions in cratonic shales, it seems likely that detritus is thoroughly mixed during weathering and sediment transport and that the REE patterns in shales reflect the average REE pattern of the sources, regardless of the ratio of clays to heavy minerals in the shales. Shales, suspended river loads, and near-shore marine sediments all have broadly similar REE patterns, and reported HREE depletions in the latter two groups may reflect incomplete dissolution of heavy minerals during sample preparation. REE distributions in shales and suspended river loads determined by INNA are similar to those in average upper continent crust, and REE distributions in shale averages NASC and PAAS seem to be reasonably representative of the average composition of post-Archean upper continental crust.