Rare Earth abundances in some basic rocks

Rare-earth (RE) abundances are reported for several basalts, diabases, and gabbros. Compared with the RE distribution in chondritic meteorites, continental basic rocks are characterized by an enrichment of the light lanthanides. Intrusive basic rocks have lower RE contents and less fractionated RE distributions than continental basalts. Chill zones of the Stillwater and Bushveld complexes have different distributions which are Eu enriched and light RE depleted. Oceanic island basalts have RE abundances similar to those of continental basalts. Abyssal subalkaline basalts dredged from the mid-Atlantic ridge and Eastern Pacific rise have RE distributions which are nearly chondritic. There is a depletion in La, Ce, Pr, and a broad maximum from Sm to Tb. Similar patterns are found in fresh basalts, slightly altered basalts, and in greenstones. Abyssal basalts that are more alkalic are not depleted in La, Ce, and Pr. The relationship of the RE data to hypotheses for the origin of ridge basalts is considered.