Rare earth element abundances in stony spherules from deep-sea sediments

Abstract

The stony spherules collected from deep-sea sediments were analyzed for rare earth elements (REE) by direct-loading mass spectrometric isotope dilution together with examination of their petrographic characteristics. Abundances of some major and trace elements including Fe, Co, Ni, Ir, and Au were also determined by instrumental neutron activation analysis. One spherule, which does not show deep-sea alteration, exhibits a flat REE pattern (1.8 × CI chondrite) with no specific anomaly. Relatively high Ni, Ir, and Au abundances in several spherules also confirm that they are of extraterrestrial origin. On the other hand, the altered spherules show highly fractionated, light REE enriched patterns with large negative Ce and minor negative Eu anomalies. Most of the stony spherules extracted magnetically from deep-sea sediments are extraterrestrial in origin and may have been derived from unfractionated chondritic material, but they are affected by deep-sea alteration during residence on the seafloor.