Geochemistry and REE patterns for terrestrial and marine skeletal apatites from Egypt.

Abstract

The present paper reports data on the chemical composition and rare earth element (REE) patterns of terrestrial scutes of turtles and crocodiles from the L. Oligocene Qatrani Foration of the Fayoum Depression, as well as marine shark teeth from the U. Cretaceous phosphate Forma tion of the Abu Tartur plateau. Generally both terrestrial and marine apatites are carbonatefluorapatites. The terrestrial variety contains less F, less heavy metals and less substitution in Ca and P sites than the marine ones do. Post-depositional activities would have caused significant depletion in Sm, as well as other REE, and enriched the terrestrial apatites with uranium. The Marine shark teeth are poor in REE and they are relatively far over toward enrichment in light lanthanides. The tooth's enamel accumulates less REE compared to its dentine. The normalized REE patterns of the terrestrial apatites are more flat compared to those of the marine origin. The plot of La/Ce versus Eu/Sm discriminates remarkably between the marine and terrestrial apatites.