Lithologically-related rare earth element variations the Mio-Pliocene Poznań Formation (Poland)

Abstract

As so ci ate Ed i tor-Stanis³aw Z. Mikulski Con cen tra tions of rare earth el e ments (REEs) were de ter mined in 129 clay sam ples col lected from the Mio-Plio cene Poznañ For ma tion in Po land. The REEs oc cur in a rel a tively wide range from 58.2 to 1,709 mg/kg. Low North Amer i can Shale Compos ite (NASC)-nor mal ized to tal REE con tents with heavy rare earth el e ment (HREE) de ple tion were noted in most of the sam ples ana lysed. Small vari a tions were de tected in the REE con tents in the lithologies dis tin guished. Red clays are char acter ised by slightly lower REE con cen tra tions rel a tive to green and grey clays. All the Poznañ For ma tion clays ex hibit a neg ative Eu anom aly when nor mal ized to the av er age of chondrites. Val ues in crease ac cord ing to the fol low ing se quence: grey clays < red clays < green clays. The NASC-nor mal ized REE con cen tra tion curves show a pos i tive Eu anom aly. The La NASC /Yb NASC ra tio in di cates HREE de ple tion. A small vari a tion in this ra tio was ob served in the se quence green clays > grey clays > red clays. The vari abil ity of the REE con tents of the Poznañ For ma tion de creased from west to east.