Rare Earth Element Geochemistry of Northwestern Niger Delta Source Rocks

Abstract

The source rock geochemistry of trace elements especially elements that belong to transition series is fairly well known. However, data on source rock geochemistry of rare earth elements are very scarce. Rare earth elements (REEs) profile of source rock samples from the offshore fields in the northwestern Niger Delta, determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) and instrumental nuclear activation analysis (INAA) is reported. Both light REEs and heavy REEs were identified. The concentrations of the detected REEs; La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Lu, Tm and Yb ranged from 3.64 – 436.67 ppm with an average of 65.18 ppm. LREE and HREE patterns constructed from absolute concentrations and chondrite-normalized values for the source rock samples show unique signatures that are diagnostic of genetic origin of the organic matter. This indicates that REE will be a useful tool in oil–source rock correlation. Concentrations and ratio of the rare earth element were found to be useful in determination of origin and depositional environment. Statistical evaluation of the REEs data by cluster analysis showed REEs as good discriminating tools to classify organic matter.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015